The main rival to CQ's Politics in America is National Journal's "Almanac of American Politics". I find them complementary. The 2010 edition is due to be published this month. The Washington Post Review has commented in the past "Indispensable . . . this compendium of statistics and information has gone as far as humanly possible."
I have bought and use both. I'm sure that as soon as copies arrive in the UK I will be ordering the Almanac