For any one of a number of reasons, we are sometimes put into a position where we need to scan our network for other devices and IP addresses. While this can be done from the Command Line using Terminal, there are two excellent scanning utilities that can be used to discover devices on a local area network (LAN).
The first Mac App is iNet from BananaGlue. iNet is available in the Mac App Store if you are running OS 10.6.6 or higher. The second Mac App is IP Scanner Pro - also available in the App Store on your Mac.
Both provide excellent functionality and a quick picture of devices and services on your network.