Blender an open source 3D modeling and animation package.
I think it is the greatest thing since sliced bread because:
Free! Compare that to the competition...
No Restrictions: Personal or commercial projects, no problem! No watermarks, no greyed out features...
Powerful: Huge Feature Set; In the hands of a skilled artist, this is a tool capable of professional quality work!
Transferable Skills: If you are just getting into 3D, free is a great place to start, and all the concepts and techniques are transferable to other graphics packages (that is - if you really want to use anything else).
Support: Blender has a huge following and very friendly online community. There are lots of user created free tutorials, model and material archives, and helpful people in chat forums to answer questions if you are stuck.
Portability: It is a fairly small download, and you can throw it on a flash drive and take it anywhere!
Great Origin: Like me, it comes from a Dutch background! And who doesn't like the Dutch?
I made all my 3D CG work with it, and have taught some blender workshops.
Want to learn blender on your own? Start here!