Take a look at the range on Overclocker's website - its nice and easy to browse so you can find one you're interested in, and their range is pretty good.
http://www.overclockers.co.uk/acatalog/Cases.html
I'm planning on picking up a Thermaltake Armor case at some point - fairly utilitarian looking but in a good way
Tips for choosing? Just read plenty of reviews I guess. There are loads of hardward modding sites that focus on cases so if you spot one you are interested in, just get on google and search for it and add +review -compare.