Project- Joining two power supplies
I assume you're talking about some kind of wall-wart type power supply, right?
You can probably obtain a 5V power supply module (assuming the pandaboard takes 5V) which has terminals to connect the incoming 120V power to. Then you would merely need to tap into the power wires inside the fridge, and connect to the input of your power supply. Bonus points for adding an inline fuse of about .5 to 1 amp.
Usual electrical safety rules apply; make sure your method of tapping into power is safe, and won't come loose or short out.
All this assumes that this is a one-off student project, not intended for permanent use.
If you're not comfortable dealing with 120V power, I'd get more experienced assistance, or stick with the power strip idea. 120V can kill.