Some interesting art-related sites include the comprehensive but rarely updated Surrealism Server (link updated to new address), Brownflower, where much interesting stuff, including a great deal of 'the new surrealism', is located.
Some roadside art in America can be found at here...all manner of beautifully decaying signage, bizzare outsider art environment and the like! Nice. The statuesque SITO, a place of collaboration and exhibition for all, and
Ed Kienholz; now he's buried in his car, but once he made very fine and very nasty sculptures and installations. Look, here.
A load of Mail art links are located at the bottom of my mail art page.
Discover, as I have, the wonders of FLUXUS: the forgotten, but enormously influential and still alive (anti-)art movement that's fun for all the human race. You can detect it in the Fluxus Indian Museum, Fluxus Online, Fluxus Portal, the Fluxus Bulletin Board and, along with surrealism, triumphantly permeated throughout the fabric of (post)modern society.
More sites by or devoted to particular artists can be found on my people page, and links pertaining to robotic, interactive, scientific and generally technological art can be found on my technology links page.