Actually, I think a caipirinha is very much like a mojito -- except its made with cachaca instead of rum. Both liquors are made from sugar cane so it's not surprising these mixed drinks are so similar, but I don't know what's the real difference between the two might be. All I know is that I liked it very much.
BTW, the locals (Sao Paulo) call cachaca by the slang name "pinga".
