LanSpy

LanSpy is a suite of networking utilities for managing a network. But they can most certainly be used for a variety of different things.

The application does a very simple thing: scan a computer host. You can, of course, define what happens during that scan. By default, it pings the host, it performs a variety of network checks and an open-port scan, both UDP and TCP. The information you can acquire from a single scan is quite useful. When I scanned a random computer on my network, I received information about the local time on that computer, about what version of windows they had, the MAC address, how many ports they had open, when the system started, what kind of shares were active, and a lot more.

And that was just scanning a computer, and I didn't even input an Administrator account, so a lot of the scans failed. From what I could gather, the application doesn't support host names. You have to input the IP address of the computer that you are targeting instead.

If you install LanSend, another application by the same developer, you can send messages to other computers from within LanSpy.

All the scans are customizable. You can change the ports that are scanned in the port scan and even add new ones. For scans you can scan a single computer or an IP-range, and results can be saved to XML files.