If you are an art lover, your life is weighed down by coffee table books. They stack up and sprawl out way beyond the intended realm. In my case, the coffee table itself rests on a mound of art books, which also mass in mountains all around. Why? Because picture books have traditionally been the only way to keep good reproductions of art with you. In recent years they have got even bigger, as publishers supersize their Michelangelo tomes.

So, the rise of online art resources is a liberation. I love the way great paintings are becoming increasingly accessible on the computer screen. One innovation is the new site artfinder, which offers you the chance to build your own gallery of favourites from a vast and presumably growing store of digital reproductions of great art. As always with these ventures, it is important to realise it is not and cannot be complete. I found at least one surprising gap: although it has 30 works by Watteau, the site does not include his masterpiece Gilles.

The big difference between this and other online art museums is how interactive it is. You can search the site by artist or period, or key in a specific work, but you can also opt for the "Shuffle" mode, which shows you unexpected works you may never have seen. You are invited to post comments on pictures (there is a Facebook plugin), or press the "Share" button and send links by email or Twitter.

Another enjoyable option is the "Magic Tour", which responds to your choices from a selection of works by offering a surprise bag of paintings of the same ilk. I quickly found myself seeing pictures I did not know. It is fun to learn about art here – there are even helpful texts on the major art styles – and the aim is clearly to create a community of art lovers around itself.

Its real weakness is that conventional online jpeg images are not very sharp and look rubbish when you enlarge them, which is why the increasing availability of high definition images is especially exciting. Google's Art Project has made the splash here but, if you have an iPad, there is also a growing choice of apps that are the virtual, weightless equivalent of coffee table books.

Yet there are still huge fields to be explored. It is frustrating that more, faster, cheaper remains the internet's prevailing logic. A decade ago, museums were producing CD-Roms that gave deep, engaged access to aspects of their collections: I would like to see that approach extended to websites and apps. Why is there not yet a really rich, interactive digital edition of Leonardo da Vinci's notebooks? These magical documents cry out for a digital encounter that lets you move from the original to a translation in an instant, while giving you high definition images of the pages with their wondrous drawings and mirror writing. Artfinder is another fine way of skimming the surface of art history. What the web needs next is a deeper exploration of great art.