Netbooks

GURPS Discworld bye Nighte
A GURPS Discworld expansion for the darker side of Ankh-Morpork and Sundrye and Fyne Partes of the Dyske.
http://www.byenighte.com

GURPS Shadow World Project
An adaptation of Iron Crown Enterprise's lost-but-not-forgotten fantasy world.
http://www.secretmasters.net/wrathchild/shadow/

GURPS 3x3 Eyes
A fan-worldbook for gaming in the 3x3 Eyes manga series by Yuzo Takada.
http://3x3eyes.sioc.org/index.en.php

GURPS X-Files
A worldbook in Adobe Acrobat format by Gawain Jones, based on the fortean/mystery TV show.
http://www.geocities.com/adriangawainjones/

In Nomine to GURPS Conversions
GURPS conversions originally written for the In Nomine core book, these predate the new GURPS In Nomine worldbook, and provide an alternate (now unofficial) approach to In Nomine in GURPS.
http://www.sjgames.com/in-nomine/gurps/

Net.GURPS.Characters.Book
A huge library of GURPS characters, ready-to-play.
http://www.sjgames.com/gurps/characters/

Rico's GURPS Humanx Games
A large and growing collection of resources and expansion material for GURPS Humanx, including adventures, character adaptions from the novels, and starships.
http://www.geocities.com/deddicus/gurphuma.htm