Have you seen Rob Galbraith's site? Look for the CF Database - speeds of cards are tested with different cameras.

IMO, the cards themselves are really commodities. The thing that separates one from another is the service that the company provides. Lexar was great when I had a problem with a new card, and I've heard good things about SanDisk. Others are out there too, but these are the two names I always hear about people using. Shop around, the prices can vary a lot.