The app runs from the system tray. When you first start it, right-click its icon, choose 'Select Config File' and choose the Sample.ini config that comes with Samurize. While this sample is relatively simple, at a minimum you'll still want to read the program's online tutorial before you try to customize it or make your own.
If you do put in the time to learn its ins-and-outs, Samurize allows you to create a huge range of meters for checking drive space, memory usage, or laptop battery charge, for instance. You can decide whether they display graphs, text, or bars, and choose where they'll sit on the desktop. You can also create or download custom scripts for checking a server's status, getting weather reports, or pulling in RSS feeds.
There are plenty of already-made layouts and scripts available from Samurize.com, but have a care when you try them. When I downloaded one named MolD3v and tried to open it in Samurize, the app crashed. It wouldn't start back up again until I uninstalled it, deleted its program folder (it leaves configs and some other data behind), and reinstalled.
Samurize may be well suited to programmers and other major techies willing to learn its foibles in exchange for being able to create just-right monitors. That said, if you want desktop widgets more suited to the average Joe you might try Google Desktop instead.
Note: Samurize is free for personal use. For commercial use, its makers require a $5 donation.