With simplewallet type in "incoming_transfers", without the quotes, and it will give you a list of incoming transfers along with the their transaction ids. For outgoing I'm not sure because I never did one. Maybe you find out when you do the transfer. The GUI wallet must also give this information. You will notice that each transaction is broken up into several transfers, the reason for this having to do with anonymity.

As FasterStronger has said, you can find this same information in "simplewallet.log". That is a text file located in the same folder as the simple "simplewallet" executable, at least that's how it is in Linux.