Dawn,
No pudge brownies are a product. You can find them at Trader Joe's, some other stores or order online.
I only wish they were vegan, oh well
I almost forgot to say what I've used plain yogurt for..
Right now I'm loving plain unsweetened (soy) yogurt mixed with 1/2 cup of blueberries and mixed with 1 serving of a whole grain cereal.
As far as substitutes, I've substituted yogurt for mayo in recipes before. It adds a bit of the creaminess without the fat.
That is all I can think of