ANGRY IP SCANNER

Angry IP scanner is a very fast IP address and port scanner.It can scan IP addresses in any range as well as any their ports. It is cross-platform and lightweight. Angry IP scanner simply pings each IP address to check if it's alive, then optionally it is resolving its hostname, determines the MAC address, scans ports, etc. It also has additional features, like NetBIOS information (computer name, workgroup name, and currently logged in Windows user), favorite IP address ranges, web server detection, customizable openers, etc. Scanning results can be saved to CSV, TXT, XML or IP-Port list files.

You can dowload it here http://sourceforge.net