I've just been introduced to a new site: Artlex. Its a dictionary for artists giving the artistic terms for words rather than their conventional usage, and specialising in formal manufacturing terms and art movements from what I can gather. Its not an amazing tool for people who've come through the art education system but is very useful from a pedagogical perspective and for those still in the throws of it. It is also suffering from a design that was looking a little ropey in 1996.

For a more conceptually useful resource try john lechte's 50 key contemporary thinkers (sorry - only found it at amazon.co.uk), and his more recent key contemporary concepts, as well as the classic Keywords by the late Raymond Williams.