You need 2 resistors of equal resistance, connected in series, resistance => 150 Ohms.
But seriously, you'll have to be a bit more specific as to the environment, + power & efficiency level wanted..
we sell a kit that does exactly this. 12V input, 5V output (although I can modify it to give 6V output) 500mA. Is this of use? see my username for a clue as to the web site address!. Let me know and I will modify one for you
Bill
Electronworks Ltd - electronic kits for education and fun
a LM317 and some resistors and perhaps a couple of smoothing capacitors will do nicely for this as well. but if your not up for doing this perhaps you should hit bill up and have him take care of you.
