Rick at Frugaltravelguy.com has a database that Howie created. It is on the right margin of his blog about half way down. It isn't updated with the current Citi offer (75K or 100K), but will give you an idea of the different cards/programs with bonuses out there besides the big three.

Pgary at frequentflyermiles.com also has a pretty good list of all of the cards/programs out there.