Free, easy to use network IP address scanner

I've used Angry IP Scanner numerous times to search for devices on the networks I manage. It's a really nice tool to have, and since it's free there's no reason not to. In fact, I've used it twice this week to figure out what IP addresses a couple of devices had after getting plugged in to the network (they were using DHCP). It works great for identifying those devices and active hosts, which cuts down on time trying to guess or having to gain access to the DHCP records to get information.