this is my first instructable a longgg timmeee, and in that time, I have learned much, such as soldering is a good thing, melting plastic is a bad thing and that using the correct components mounted on a board is a good thing.
But less of that and on with the instructable.
Step 1: Components
9v Battery Clip OR DC Jack
9v Battery OR ~9v AC-DC transformer
0.1uf capacitor (or 100n capacitor)
L7805CV 5v regulator (..or pretty much any other 5v regulator)
assortment of wire
a heatsink for the regulator (optional)
old piece of board
Step 2: The Schematic
This is what you should build it from.
Step 3: Test It!
Grab your multimeter and hook the positive up to the positive, and the negative to the ground. Don't forget to set it to VDC at the correct range.
I tend to use this for testing and because I had this regulator lying around, but you could hook up a female usb connection to charge up your phone or something (won't work with iPhones or iPod touches without a little modification)