Recently the 500th MOC has been uploaded to the site: this beautiful Mercedes-Benz 540K roadster from Sariel. Since this is a remote-controllable car you need two motors as well. The full building instructions can be downloaded from Rebrickable.
There are many other great creations, even some Technic ones like this Sunbeam Corvette supercar with pistons, suspension, gearbox as one would expect. The instructions for Jurgen Krooshoop's model can be downloaded from here:
There are planes too. This Pilatus PC-21 has been covered on TechnicBRICK as well, built by Ismaël (Khan) Juhoor (download link).
These models are all very professional, but building them at home will need serious preparations. The part list is usually available, but it is quite likely that you will not have all the parts and have to buy new ones.
If you would like to simply play, Peter Sprogis has uploaded many models that can be built from a single LEGO Creator set, like the 4939, 5867, 6743or 6913. For example this pickup truck:
It is worth going through the list.
I think Rebrickable is one of the best things that have happened to LEGO during the recent years. The site itself is not blazingly fast and could be more helpful in discovering new models, but to see the instructions for many cool creations makes it one of the most interesting LEGO sites over the Internet.
