I'm not a huge sabermetrician, but that's because I don't really have the time to read up on everything. I'm a big fan of them though, just wish I knew them better.
The one book I have, and I think it's great although it can be a bit confusing at times, is Baseball Between The Numbers - Why everything you know about the game is wrong, written by the Baseball Prospectus. I highly recommend this book. It's easy to navigate and you can learn a ton.
I also find this article by Bill James comparing Adam Everett to Derek Jeter defensively to be quite a great read as well.
Anyone have any suggestions for books? Moneyball is another obvious one.