Bread-Bakers v106.n037.1

I was reminded by Mike's informative posting that I have a question: 
Can anyone tell me how to substitute starter for yeast in recipes for 
things like pancakes, pizza crust, muffins, etc?  What volume of 
starter?  Do you modify the other ingredients?  Do you let the dough 
sit and proof before baking?  I've baked lots of sourdough bread, in 
fact I almost never use yeast, but I'm hesitant to branch out and try 
other things without some guidance.

Thanks,
Deborah