There is an article on Torrentfreak (http://torrentfreak.com/which-vpn-pr...iously-111007/) what talks about what VPN's you actually are anonymous on (who keeps logs)
To summerize that one, you should by all means AVOID:
VPN providers that are known to not keep logs, on other words RECOMMENDED are:
That's a short summary for you guys. If you plan to buy a VPN, i'd recommend reading the whole article anyways.
EDIT: TorrentPrivacy removed from recommended according to GregorSamsa's comment.