The Turtle Moves - An internet community that roleplays in the Discworld setting through posts in their message boards. - http://www.theturtlemoves.co.uk/
GURPS Discworld bye Nighte - Expansion for the darker side of Ankh-Morpork, Sundrye, and Fyne Partes of the Dyske. Uses a forum for discussions. - http://www.byenighte.com/
The Truth - Guide to Ankh Morpork and its guilds, information on Pratchett, and an image gallery. - http://www.ankhmorpork.iwarp.com/