Use Cryptsy we just celebrated our 3rd Birthday, and still going strong! You can buy numerous altcoins as well as Bitcoin.
sometimes deposits are too slow there(and withdrawals too), it's that fixed already? because despite this there is a huge volume which make cryptsy an interesting exchange for moving big amount
Cryptsy and huge volume? Title says Bitcoin exchange. Cryptsy volume is generated by altcoin trading. Their BTC/FIAT volume is not even worth mentioning.