Can someone help me identify this bicycle?
BikePedia has an entry about a bike that looks to be the same as what you posted.

It's a Cannondale Adventure 400 femenine model.  It appears that this came with a front shock initally, but may have been fitted with a rigid front fork (or there were alternate models without the shock).  

These appear to have been produced for several years, with a mostly similar design. I'm not quite sure what year that model is.