Here's a book I wanted to point bassists to, as it's an excellent resource and hard to find. It's the Reinke edition of the Sevcik bowing exercises, a very thorough method for practicing bowing, focusing on different areas of the bow with varying bow speed and articulation. I've been working with it for the last year or so, and wish I knew about it earlier.
Sevcik Bogenstudien (bowing studies), Reinke ed.
There's another edition of these etudes called Strokin' (apparently edited by Hal Robinson). I've never had a chance to look at that one to see if there is any appreciable difference. If anyone has an opinion about it, feel free to contact me via email or comment ("comments" link is below).
If you do use the link above to order the Sevcik from Sheetmusicplus, be prepared for a longer-than-usual wait: it's a European import and takes a little while to ship.