gracz54 has released a little app to change the MAC address of your PSP.
If you download this, there's only one Eboot around. For the newbies, this means that if you're firmware requires two folders of the application, then you'll have to use PSP brew.
Another thing to be cautious about is that its only been tested on 3.02 OE-A. For some run-through on the installation, Just paste into psp/game150 (or psp/game). And then, run the app and press X to dump the MAC ID. Once you've grabbed a hex editor, you should be able to see your MAC in hexes at the beginning of the file.
You may actually change the MAC to whatever it is you'd want to be, but DO NOT TYPE IN NEW CHARACTERS or change anything else EXCEPT THE MAC. Why? Because it could brick if you do not heed this warning.