I did not find this little board but saw it posted by another member. I bought some and have done some testing. So far I have powered a MR
board, buck puck, and a cheap hasbro board + P4
(using pololu board to power the p4 so there is no clash flash). All with great success (well except for instant on and off with the hasbro combo).
Here is a link to the board http://www.pololu.com/catalog/product/750
There are two versions of the board so get the correct one for your application (I would go with LV on MR boards and SV on buck pucks). If you just want to get one version I have tested the SV and it works down to 3V but not sure if it will cause it damage.
Here is a diagram I made to help out on hook up to a MR board.
Here it is for a puck (same picture but wiring text changed)
Hope this helps someone.
EDIT: I didn't mention one thing in the write up. To use this in conjunction with a economy hasbro board (the new ones at least) you have to use a DPDT switch. The hasbro board has one of its pins connected to ground so it messes up the function of the pololu board (makes it on all the time).