Advanced Player’s Guide published by Expeditious Retreat Press for Dungeons & Dragons 4E.
Credits: The entirety of the book, save for the Craft’s system and a few tweaks by Owen K. C. Stephens.
Notes: An enormous undertaking, intended to bring a lot of past-edition options into 4E. This includes variants on old races and classes, designed to work with WotC’s upcoming plans (so far as I know them), rather than against them. A tough project, but one I’m immensely proud of.