Go to town.hall.org/radio/HarperAudio and click on Wallace Stevens. Click on the first file. You will hear the voice of Stevens in old age reading The Idea of Order at Key West, one of the most perfect poems of our time – no, of any time. A shiver ran down my spine when I first did this. I’d never heard Stevens’s voice before.

Not into poetry? Okay, go to YouTube and put “Picasso” in the search box. Click on the video entitled “Picasso is painting . . .” You will see a scene from a French documentary, showing a wry, half-naked Picasso dashing off a very odd picture. You prefer the history of ideas? Input “Foucault Chomsky”. The first video shows Michel Foucault and Noam Chomsky debating on Dutch television – well, not so much debating as conducting competing monologues. As dated and absurd as a tank top, this, nevertheless, is the authentic sight and sound of two deluded giants of postwar thought attempting to make history. Or put in Heifetz and watch that great violinist play the Bach Chaconne. Or put in Samuel Beckett and watch Jeremy Irons perform Ohio Impromptu. Or – superb, this – put in “Lee Marvin John Ford”. The first video will show you the actor explaining how Ford got the best out of his cast in The Man Who Shot Liberty Valance, a sublime movie.

The internet is now 19 years old – dating its inception as a mass medium from Tim Berners-Lee’s invention of the world wide web in 1989 – and it is finally growing up. Popularly, and more or less correctly, it is still assumed to be dominated by geeks, porn, stoned students and assorted hucksters. It is also correct to assume that it is, not to put too fine a point on it, “full of crap”. Bonkers blogs, corporate/political hype and the whole undifferentiated melee of bad pop, worse television and inane celebribabble still make surfing the net a slightly less culturally respectable activity than watching The Big Food Fight on Channel 4. But something has changed. Basically, this is because of the techie phenomenon known as Web 2.0 – more interactivity, more user-generated content – and the failings of mainstream media. The first we can take for granted; the second may be less immediately obvious.

In an important article, Alex Ross, music critic of The New Yorker, observed: “Between 1980 and 2000, classical music more or less disappeared from American network television, magazines and other mainstream media, its products deemed too elitist, effete or esoteric for the world of pop.” The same applies to all expressions of high culture. Over the past 20 years, the increasing power of marketing and advertising over editorial has driven the mainstream ever further downmarket. I know, in the midst of this decline, we get quality pop products such as The Simpsons and so on, and I know there are plenty of specialist outlets. But that is not the point. Much that should be routinely available is excluded from the mainstream, crowded out by the short-term demands of the bottom line. The fear is that this crowding-out will lead to a severe case of what Clive James calls “cultural amnesia”: starved of popular acceptance and in a climate of perpetual novelty, high art will simply be forgotten.

Riding to the rescue is, first, an economic theory. The phrase “the long tail” was coined by Chris Anderson, editor-in-chief of Wired magazine. Order an obscure book from Amazon and, with luck, it will arrive the following day. This is worthwhile to Amazon because there are millions of obscure books, and, even if there is only one customer for each, that is still millions of customers. In other words, technology makes it possible – Amazon needs only a web page, not a shop – to profit from the previously ignored “long tail” of the sales graph. It is thus no more difficult to buy Claire Guimond’s recording of Telemann’s Fantasias for Flute Without Bass on iTunes than it is to buy the latest by Arctic Monkeys. There are many arguments about the significance of the long tail, but I was once told by a Waterstone’s executive that it was nonsense, so it must be true.

The second saviour of high culture is an aspect of Web 2.0: interactivity. People put comments on YouTube videos. One clip on it is a reading of Stevens’s The Snow Man – there seems to be some dispute over whether this is Stevens’s voice or not – over shots of a snowbound landscape. Here is one of the comments: “There are a certain very few things [sic] in this world that keep me alive, almost compel me to live just by popping into my mind at the very last moment, in spite of the most unbelievable suffering that I cannot put into words: the poetry of Wallace Stevens is one of these things.” I’m with you, franco6719, aged 40, from Italy.

The point here is that the consumers of the long tail are no longer alone. This often produces the most gratifying results. I mentioned the novelist Marilynne Robinson on my blog once. A writer in LA immediately asked me what he should read. A couple of hours later, he came back to tell me he’d bought her novel Gilead and read a few pages. I was right, he said: she is a genius. Or try a site called The Garden of Forking Paths (gfp.typepad.com/the_garden_of_ forking_pat ). This is a philosophical discussion blog, largely about free will. I got involved with this for a while, then had to stop, realising I would have to devote most of my days to keeping up. Then again, why not? There are many such blogs. Find them by visiting Technorati.com. It’s slow, clunky and poor on updating, but it scans most of the almost 100m blogs of the world.

Interactivity gives the long-tailers two huge benefits. First, it frees them from the prison of the mainstream and having, for example, to wait for years to see a television documentary on Wallace Stevens or Jascha Heifetz. Now they can find the material whenever they like. Second, it gives them what they need most if they are to survive – community, a sense of belonging to something other than the culture of mere distraction.

The final and most obvious boost to seriousness on the net is scale. Download speeds are now fast enough to make streaming video and audio easy. More important, the net itself is now so vast that, to a rough approximation, everything is there somewhere. This transforms the nature of knowledge and expertise. Say that a few words from a poem come into your mind. Type them into Google and you’ll have the whole poem in a fraction of a second. Ten – or even five – years ago, you would have been clutching your head for hours. Apply this to the visual arts and we can get rid of those awful headphone sets galleries provide. Much more can be learned about a painting by simply firing up your iPhone while standing in front of it. All the gallery need do is provide WiFi: not much to ask.

We risk drowning in this info-ocean, however. Knowing everything is not much different from knowing nothing. Judgment, therefore, rather than brute fact-finding, is the key. The trick is to narrow your focus, to decide exactly what you want to know and to refine your sense of what is serious and what is not. This is not easy. It takes time. You can lose hours taking nonsense seriously.

So, here are a few serious net delights – there are millions of others. The contemporary visual arts are, predictably, well served: the net is, after all, primarily a visual medium. Frieze is now as much of an online presence as it is an art fair. Frieze.com tells you more than you need to know about contemporary art. Should this inspire you to become an artist, you can register at Saatchi Online and instantly expose your work to the world. Failing that, the site is an extraordinary glimpse into what people, rightly or wrongly, think is art these days. With Banksy, the site becomes the art; banksy.co.uk is studiedly cool and offhand, but funny.

Music is now sensationally well served. The record label Naxos (at www.naxos.com ) is challenging the iTunes download model with a subscription system that gives access to its entire catalogue for $19.95 (£10) a year. Alex Ross pointed me to two amazing sites, www.schoenberg.at, an exquisite shrine to the composer – I love the idea of his work being available on a web “jukebox” – and keepingscore.org, the site of the San Francisco Symphony. This gives web, radio and even pages where you can follow the score of the music being played bar by bar.

Right, now you want to learn the violin. You can at theviolinsite.com . Once you’re getting good, check your progress at music-scores.com – all the sheet music, and what it sounds like.

Literature, thanks in part to Amazon, was the art that first took off on the net. There are thousands of good book sites and blogs. Books, Inq is a blog produced by Frank Wilson, the literary editor of The Philadelphia Inquirer, which assiduously points you in the direction of countless literary links. Jenny Diski (jennydiski.typepad.com ) and Susan Hill (blog.susan-hill.com ) produce good examples of writer’s blogs, though the latter recently made the rooky blogger’s mistake of including pictures of her cats. And there are thousands of highbrow literary fan sites and blogs. To stay with Stevens, try The Dao of Wallace Stevens. I recently found, to my amazement, that there was a blog devoted entirely to the great Edwardian literary agent JB Pinker (pinkertheliteraryagent.blogspot.com ). And there are two big literary sites that work as guides to the book net (complete-review.com and readingtheworld.org ).

I could go on, but the point is clear: it’s all out there, from a video of Heidegger on YouTube to all the sheet music you’ll ever need for your euphonium at music-scores.com. The web is what you make it, the long tail is what matters, and all you need to make sense of it is what Stevens called a “blessed rage for order”. And you don’t have to take my word for it – you can hear him say it now.

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