I tried the idea from the tightwad gazette for egg substitute. You use a tbsp of soy flour with a little bit of water and it worked great in the cake we made. The soy flour was $6.99 for a small bag, but It should last me about 6 weeks. It will save me money in eggs, because when I buy eggs everyone starts making egg sandwiches, scrambled eggs, etc so they disappear pretty fast. And nothing is more annoying than buying eggs for baking and when you start baking you realize you have no eggs.

Here's another one that I use since I always have Flax seeds on hand.

    *   1 tablespoon ground flax seeds
    *   3 tablespoons water

Mix together until gelatinous.  Works well in any recipe where there is already baking powder or such for leavening.