The Best Egg Substitutes for Any [emphasis mine] Recipe
Hmm, I want to see more research on this one. Muffins, pancakes, sure, but how about butter cake?
Also worth reading the comments to the article. I liked the one about scrambling some soda water to go with bacon

Seriously, though, some of the failures seemed to be multiple substitutions (applesauce for oil, gluten free flours, etc.) which may have been too many variables to adjust all at once. And the brownie failure was pretty obviously due to the lack of emulsifier in the missing egg yolks.