Using a USB socket does make it easy to connect power, that's for sure. The battery "power banks" for extending cell phone talk time work great to power a PIC circuit too, so you can easily make something portable or take it for show & tell.
Most of the time, for more quick & dirty development work, particularly with a breadboard, I usually just cut the end off a wall wart and graft DuPont connectors to each wire. If you do this to a USB cable, you can still plug in into a USB wart wart, computer, or battery for power.