According to this article at hardball times, Kemp had the best CF arm, and perhaps the best arm in baseball last year.  This was surprising to me, as I knew Kemp had a good arm, but I wouldn't have guessed that he'd have the best arm in the league.  Of course, I didn't look too in-depth into the stats, and wouldn't really know how to read them (I'll leave that up to Eric) but an interesting article, nonetheless.

http://www.hardballtimes.com/main/article/best-outfield-arms-of-2008/