While this is a few days old, I'd be remiss if I didn't mention their latest update. I won't copy and paste the explanation - just click the link, stupid - but long story short, now they provide some data for batters based on pitch location, like %pitches in the zone and %contact on pitches out of the zone, that provides a lot of insight into which guys have plate discipline, and which guys simply flail away. Go check it out.
Just a few things I found interesting while messing around:
-Jason Giambi has a good eye
-Carlos Gomez doesn't
-Reggie Willits never swings ever
-Todd Helton possesses an extraordinary ability to make contact on everything
-Juan Pierre does too but his contact sucks way more
-For a good hitter, Kevin Youkilis gets thrown an awful lot of strikes
-Adrian Beltre is seeing far fewer strikes than before (and he's laying off of more balls)
-Kenji Johjima is doing worse despite what so far has been an improved approach
Between the awesome amount of detailed information and the much-improved front page blog, Fangraphs has become a place you ought to visit several times a day. What a fantastic website.