James Ernest has written an interesting blog post on how the early Cheapass games were produced.
Vexillia has a selection of free flags for various European armies from the 14th, 15th and 16th centuries. These include 100 Years War, Wars of the Roses, as well as Spanish, Swiss, Landsnechts, Savoyed, Venetian and Imperialist.
Look in the right hand sidebar on the page for the links.
Mantic offers a free download of its Warpath Science fiction rules.
Mantic offers a free download of its Dreadball rules for science fiction sports / combat.
Fascinating stuff for history buffs ... which I assume most of my readers are ...