I’ve recently started playing around with the FEZ Spider kit. I am wondering what others have used as an external power source.
Has anyone built your own power supply?
Building your own power supply is a bad idea unless it is 200mA! When you need 1A or more or more than it is better to just get a power pack. Plus you will be saving a lot of money as power packs are VERY cheap http://www.amazon.com/Power-Adapter-Supply-2-1mm-CCTV/dp/B00452YFZU/ref=pd_sbs_op_3
Thanks for the link. I have many power supplies laying around I think I could salvage. I was hoping to make this autonomous and make it run off a power pack that could be recharged when needed. I am just nervous about putting too much power (or too little) to the device and breaking it as I know little about power.
If you are using USB Client DP module, look on the back and you will see 7V to 30V. I can’t see any way you can damage the module with 12V power pack. It even has reverse voltage protection in case you got the wrong pack 
Is the 2.1mm barrel jack from amazon the correct size for Cerbuino Bee / Gadgeteer DP supply?
Yes.