I've been going through Google's 3D Warehouse to find cool models that people have designed, but not necessary had 3D printing in mind.
The first object that really peaked my interest was of the Great Sphinx. Always with my 3D printing hat on, I quickly realized it's a great candidate for 3D printing since it basically solid, has a large flat base, and doesn't have wild hanging or cantilevered parts.
I used combination of Google Sketchup, and some plugins to export to an STL file. Then brought this into Blender 3D to clean up the model, smooth out the polygons, and remove extraneous ones.
Loaded that up into ReplicatorG, sliced, and printed. Here are the results:
Great Sphinx by jwolee