If so, then look up sourdough here.  There are some excellent entries about starting a starter and making sourdough bread.  But if you mean yeast free as in commercial and wild yeast free, then all I could know is quick bread recipes.

What's wrong with yeast?

Yeast free breads would be leavened by chemical methods such as baking soda (sodium bicarbonate)  - like Irish soda bread.

They tend to get stale pretty quickly, though - I like them, but nothing beats bread made with a nice, active, bubbly yeast culture, the wilder the better

true yeast free breads are quick breads such as southern corn bread and the not so quick boston brown bread  (1 to 2 hour baking time)

The only non-chemically leavened but yeast free bread that I can think of right off hand would be a real salt-rising bread which does not use a yeast fungi to generate the necessary gas.  I've read about it, but have never tried it myself. 

http://en.wikipedia.org/wiki/Salt_rising_bread

Sourdough usually doesn't have the same species of yeast in it that is commercial baking yeast, but it's still a sacchromyces species so far as I've read.

.....Alan.