I bought this one: http://www.ebay.com/itm/500-x-0-01g-Digital-Jewelry-Scale-Gram-Grain-Carat-/320833253772 and it works for me. Fast shipping and I've dropped it several times and it still works great. I'm pretty impressed with the quality for how cheap it is. But it is only accurate to 0.01...
I have this book and I reference it often: American Ammunition and Ballistics by Edward Matunas.
It basically goes through every caliber and evaluates it (partially based on the author's opinion, but also based on testing velocities, etc). I'm sure there are more like it, and this one is old...