It seems like there are more than a few fantasy football players here, so where does everyone get their information from? Besides the regular sports sites like espn.com and foxsports.com, I usually use rotonews.com. Rotonews has sone decent information, but I expect that there are more detailed sites out there.
For the best overall info, looks and playability, I like Full Contact Fantasy Football on http://www.sandbox.net
Yahoo is a little uglier and slightly less player-friendly, but works well also.
For the first time this fall, I’m also in a league on http://www.nfl.com, in addition to the Straight Dope Sandbox league.
As you might imagine, a league sponsored by the NFL offers you an incredible amount of data. You can break down stats for your team, free agents, etc., to an incredible amount of detail. But I’m surprised that I don’t really like it as much as Sandbox for a lot of other reasons.