Not many know that Pentax is backward compatible to just about any K mount or M42 screw mount lens you can find, all enjoying image stabilization with full meter readout.
The kit lens (18-55mm) and kit tele zoom (50-200mm) are pretty good. As is the excellent and affordable 50mm f/1.4 http://www.popphoto.com/cameralenses...mm-f14-af.html
The new Pentax DA* 16-50mm and DA* 50-135mm are both excellent f/2.8 zooms as are the DA or FA series prime lenses. Compact in size yet the image and build quality are first rate.