[chas123]

I take no credit for this. I found it archived on an obscure forum while searching for something else. I tried to find it again so that I could give the author credit, and couldn't.

Instructions:
1) unzip the files into your Android sdk tools folder.
2) Open the testsign_apk.reg with Registry Editor

Now when you right click on an apk file there is an option to "resign apk"