New project alert: Tome of Trade.
Tome of Trade will be a d20 sourcebook compatible with Dungeons and Dragons e3.5 (PF players, there shouldn't be any stumbling blocks in using it there as well). It will be available in PDF format only.
This book will contain large amounts of content made to allow playing the market. Classes, spells, items, a whole system for handling running a shop.
The project is launching today, and will run until the 23rd of March. More details can be found here.