You can try this IC from National Semiconductor LM2576.
http://www.siongboon.com/projects/20...c-dc_converter
It will not generate as much heat as 7805 regulator.
LM2576 can power up to 3A, enough for most electronics.
Input can be from 7Vdc to 40Vdc, and output is regulated at 5Vdc.
Other version of LM2576 are available with 3V, Adjustable output voltage, and more...
Have fun.