From The Eldon Waldo:
Finally, an IP Subnet Calculator. Minimizes to a nice little bar, supports traditional and CIDR notation and generally goes about its business of calculating subnet information.
Use the mouse, tab, or full stops to switch between fields and hold ctrl or the apple key when clicking the small bar to move the window around. When in full mode you can click anywhere in the window space to move the window normally. The color is customizable to suit your mood. This version is the first release on CNET Download.com.