Advanced IP Scanner
Need a quick and no-fuss way to list every device on your network, including the IP address and other information about each? Then give this small, free, simple-to-use utility a try. Advanced IP Scanner v1.5 performs a lightning-fast scan of all IP addresses on your network, or of all devices in an IP range you specify. It then tells you what devices are at what address, and lets you know whether the devices is currently live or idle. It also provides the device's status, machine name, NetBIOS information, ping information, and MAC address of every machine.
Advanced IP Scanner includes a few other nice tools as well, including the ability to shut down PCs remotely. There's also a "Wake-on-LAN" feature that can wake PCs that have network cards that supports that capability.