+1 for Giant and Specialized, I would also like to suggest Cannondale if you are looking for a lady-specific frame.

Giant has been manufacturing excellent female specific frames for a long time, same as the other two. I'm sure there are other manufacturers as well, but I would start looking here. I think Cannondale (not sure about others) offers petite-sized frames for 29ers as well, but you should definitely give them a test ride before purchasing as they are not for everyone.

Here's another tip - try looking at last year's models (2009/2010, even) as well, you might get a nice discount without any sacrifice in quality