Private Eye is a free network connection monitor for Mac. It monitors both incoming and outgoing connections.

Features:

• 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.
• 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.
• 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.

Requirements:
OS X 10.7+
Intel