Private Eye is a free network connection monitor for Mac OS X Lion.
See connections in real-time
When an app makes a network connection, you see it instantly on your screen. There's no delay and you don't have to use a separate recording mode.
Show the connections you are interested in
Filter connections by app or direction
Interested in the connections of a single app? Only outgoing traffic? You can filter the list of connections to avoid being overwhelmed by noise.
Private Eye is lightweight
Keep your Mac fast and responsive
Close the app window, and the network monitor is automatically turned off. Private Eye stays out of the way by slacking off whenever you aren't looking.