Last Updated: February 9, 2014
Old School Renaissance Publisher's Group at Lulu
Your one-stop shop for a majority of the Lulu-produced OSR rules-sets and supplements.
Online Books Page
Your guide to online books...
Open Font Library
Many, many free fonts you can use in commercial efforts without any need to license them.
The Online Literature Network
a great place to find obscure classics and old books converted over into electronic formats.
The Old School Reference and Index Compilation. Essentially AD&D with the serial numbers scratched-off and cleaned-up a bit. This rules-set will let you use most of the stuff that was produced for the Advanced form of the world's most popular RPG, breathing new life into all those remaindered modules and so forth. It has also sparked a rebirth of sorts in a cottage industry of developing adventures for a game system that was summarily abandoned by its custodians/care-takers/check-cashers years ago.