Use them to make cookies. Here is a recipe I used. They taste great. They don't rise much so I would think old cake mixes would do okay. I've used yellow and chocolate mixes so I would think any flavor cake mix would work.
Gooey Butter Cookies Recipe - Allrecipes.com
You know I read something too...But the one I read was about pancake mix. It sounded pretty bad, but I didn't pay too much attention because we usually use up these things pretty quickly. Maybe we need to google it and see what is what.This is Craig's wife, Karen. He's not home to post but I was just flipping thru and saw this post/question. Be careful about using old baking mixes. I read something once that some kind of toxic mold can grow in them after they get past their expiration date. I vaguely remember the article or post saying it tasted, smelled and/or looked not quite right but the woman went ahead and used it and made her son really sick - as in needing to go to the hospital sick.
Karen