The 3D modeling software really depends on what the end result is going to be. If you want the end result to be animation, things of that sort, you want a high end application. If you are just looking for something to model for lets say a web site, then you really should stick with low end apps. In my experience, I have used high and low, here are some of the software packages available (Its been a while, so there may be some error in this list).
High end:
ProEngineer - Parametric Design
Unigraphics - Parametric Design
Lightwave - Excellent for visualization and animations
Maya - Another really super terrific one
Low End:
AutoCad with Accurender - 3rd party Accurender has amazing results
Rhino3d - All inclusive solid modeling from the makers of Accurender
Autodesk 3D Studio - More animation
SolidWorks
Bryce - Visualization
Macromedia Flash - Not solid modeling, but good for animations
I may have missed some, but its a start.