http://voteforpolicies.org.uk
It's quite interesting really. The site presents the policies of a bunch of parties but without their names. It kind of forces you to pick something that represents what you think over anything else.
Anyway, I'm 77% Green, with another 11% going to Labour and the Lib Dems each. I was Green for every issue apart from immigration (Labour) and Europe (Lib Demb) apparently.