Since the jailbreak community formed sometime in late 2007, we've seen a number of "App Store alternatives." I can think of Icy, Cydia, Rock Your iPhone, and Installer just off the top of my head.
Now it looks like we could soon be adding another option into the mix: iTweak. The new store describes itself as a 'Cydia alternative' where jailbreakers will be available to find all of their favorite tweaks, themes and utilities...