Mighty DBX Empires is a DBA variant for Games Workshop’s Might Empires rules.
Here’s an extremely well done unofficial army book for halflings in Warhammer Fantasy.
Aquanautica Imperialis is a set of rules for naval games in the world of Warhammer 40K.
Here’s a set of rules for converting the large scale Warhammer Fantasy battles game to a skirmish version.
ToyMallet 40 cents is both a set of fairly well-done generic science fiction rules and a brilliant parody of the Warhammer 40K franchise. Written by Jennifer Reitz, it allows you to use any toys you happen to have, instead of spending many hundreds on “official figures.” The photos of the Hello Kittau Neko-Wai Meowarriors are a scream.