Blender is a pretty fun program. I've played around with it a few years ago.
I addition to Blender, Autodesk, the makers of the applications used by professionals in the industry such as Maya, 3ds Max, and Mudbox, makes all of their student version of their software available to anyone completely free. A professional licence of this software can easily run up to more than $5k.
http://students.autodesk.com/?nd=download_center
Basic modeling should not be too much of a problem, but for anything advance I would recommend checking the system requirements. Some of the more complicated modeling and lighting can become quite a system lag.