I'm using bitcoin-qt, the one I downloaded from bitcoin.org.
That client generally enforces a fee in situations where the transaction won't relay or confirm without it. As such, the transaction will most likely confirm eventually. If you keep the wallet running, it will occasionally re-broadcast the transaction to make sure that the network doesn't forget about it as well.
If after a few days you don't yet have a confirmation, you might want to come back to the forums and ask for assistance in removing the transaction from your wallet so it can expire on the network and you can re-send it with a fee. It isn't a simple process.
