After years at Yahoo, we switched last year, and I'm a really big fan of CBS now - the FAAB $ system is great and everything can be controlled by the commish - you don't have to email anyone at the site when you want to undo a trade or correct other intraleague issues. And this year they're adding online auction capabilities to live drafts.
CBS offers a $50 rebate through March 25 if you use this link
, making it $79.95 for your whole league to play instead of $129.95. Plus you get $50 more for each referral you make to others.