LemonStand is currently in beta but looks great, very similiar to magento but looks a little simpler.

http://lemonstandapp.com/

Spree look great as well, however it uses ruby on rails which is totally alien to me;

http://spreecommerce.com/


I've had a huge number of problems finding a suitable cart for myself; I've done an oscommerce cart before and I refuse to go through that living hell again!! Once you've manually added 20 odd mods pasting line by line into the code, you'll understand.

Anyone got spree working?

I'm settling for magento at the moment