Ian @ dangerousprototypes.com
In Eagle polygons are used to make big copper areas on a PCB that aren’t necessarily traces. We use them all the time to fill blank space on a PCB with copper connected to ground. Less frequently we use them to make large power traces such as with the ATX Breakout Board. Here’s some notes on how to use and customize polygons in Cadsoft Eagle.
Polygons and ground fills for PCBs in Eagle - [Link]