Satyajeet's link above is a very nice collection of various shapes, parts and assemblies for practice with 3D modeling and drafting in CATIA or any CAD system. Not for beginners, but some good parts to test and improve your CAD skills.
Please note: The multi-view part drawings are 1st angle projections. And the assembly drawings are 3rd angle projections. This might be a little confusing to some.