if its not cannon id go for a nissin or Yongnuo
what kind of price range were you thinking of spending and do you want to be able to fire it off camera
Yongnuo YN-568EX II great flash for 120 quid and can be fired off camera with a 60D, it is a bit complicated compared to others down the line but it does do everything you will need and probably more, the early yongnuo's had a reputation for being a bit flimsy but certainly now they are robust and well made in my opinion
the YONGNUO YN560 III again can be fired wirelesly from the camera but lacks some of the features of the 568 ie ETTL but it is only 56 quid
the nissin DI622 II iand DI866 II are great flashes, powerful and well made but if you want to fire it off camera you will need to look at getting some triggers