Liber Fanatica - Great fan-made resources for v2 & v3. The early editions of Liber Fanatica focused on converting v1 material for v2, but since then the project has branched out into creating all kinds of GM and player resources. Each issue has a theme and collects together resources to flesh out that theme in the old world- background info, rules, tables, etc. There are also collections of 'unfiled' projects and maps. One of the most active current large-scale WFRP fan projects.
Strike to Stun - Another long lived WFRP site with roots going back to the v1 era. Occasional news, lots of tools and adventures to download, and a relatively active forum focused on WFRP (mostly v1 & v2). Probably the most active WFRP-focused forum around on the net.
Winds of Chaos - Tons of great tools here. Expanded critical hit tables, beautiful color and black & white maps based on Mad Alfred's work, Excel sheets to speed up using trade rules for buying and selling goods, character sheets, lots of Imperial setting info including weather tables, calendars, and food information, character generators, and more.
Critical Hit Effects - Location and damage-specific critical hit generator. Mouse over a location, scroll to raise the crit value to the appropriate level, then click on a damage type (e.g., flame, blunt weapon, bullet) to get an appropriate random critical effect.
WFRP v2 Character Generator - Quick random or semi-guided character generation. PDF export and save/load capabilities available.
Mezriss's Character Keeper - Not quire a character generator but somewhat more than a character sheet. Web-based tool for keeping track of character stats on the fly.
The Altdorf Correspondent - WFRP blog. Home to a fantastic giant multi-layered map of Altdorf, and news updates about the game and other blogs.
Mad Alfred's WFRP Pages - A community staple since v1 and the long drought before v2. Lots of materials and maps covering a wide range of topics, including a new ending for The Enemy Within campaign, conversions of v1 stuff dropped in v2, background materials, and numerous v1 scenarios.
The Bergsburg Project - Begun during the long gap between the end of WFRP v1 and the release of v2, the Bergsburg project created a comprehensive setting guide for the previously undescribed city of Bergsburg in the northern Empire. Updates seem to have died out around 2008, but the old material is still available.
Lexicanum - Fan-made Wiki encyclopedia of the Warhammer world. Includes lots of general Warhammer Fantasy stuff- the current miniatures game's take on certain regions, NPCs, and other elements is at odds with the WFRP v1 view of the world and sometime offer a different focus or presentation than the v2 version. Still includes useful general reference information on the history & geography of the Old World and beyond.