One World Mail Art Show - Good mail art site on many counts: international scope and purpose, school children's section, documentation of show and participants. Perhaps best is the "closeups" section, which includes samples of many mail art regulars. Curated by Mark Bloc - http://www.panmodern.com/one.html
Electronic Poetry Center - "The EPC serves as a central gateway to resources in electronic poetry and poetics produced at the University at Buffalo [New York] as well as elsewhere on the Internet." Emphasis on "experimental and formally innovative" work. - http://epc.buffalo.edu/
Endless Poetry - The poetry on this site was generated using a random poetry generator. - http://www.endlesspoetry.com/
Mez - Australian Mez, also known as Netwurker, writes in a code she calls Mesangelle. Samples, resume, and reviews. - http://www.hotkey.net.au/~netwurker/
Fluxus - Appropriately confusing site. Includes work by George Maciunus, and Dick Higgins. - http://www.panix.com/~fluxus
Surrealist Pages - Edited by J. Karl Bogartte. A lot of people use the term "Surrealism" carelessly, or solely in reference to French fashions of the 1920s. It's more than that -- a way of life, no less. This site is a good introduction, with plenty of links to ot - http://www.execpc.com/~bogartte
Light and Dust - This pluralistic and comprehensive site includes at least one example of virtually every form of experiment in progress over the last 30 years. - http://www.thing.net/~grist/l&d/lighthom.htm
Click Poetry - David Knoebel's sound poetry site. Highly resourceful use of sound possibilities online. Most are compact and don't require state of the art computer equipment. - http://home.ptd.net/~clkpoet/