I
will go on record and strongly caution you against too much messing
around with ingredients, especially leaveners, tenderizers, tougheners,
etc--the ingredients that lend structure and texture to your baked
goods. Sometimes, though, you just have to find out for yourself.
Many substitutions will not adversely affect your finished product,
especially substitutions of flavoring agents. I encourage that sort
of behavior whole-heartedly. So, here is a link to a very good
ingredient substitution chart.