If you want a really good free 3-D program, you can download
Blender. It was basically made from the ground, up by people who do 3-D modelling for a living, who wanted an interface that worked better for them than the other commercial products available.
Sounds great and all, but I found it tougher to use than Lightwave and Poser... though, honestly, that all is really a personal preference type of thing, so it may be perfect for you.
Also, a Wacom Tablet is, IMHO, a necessity for any original computer-based artwork. There is so much you can do with a tablet that is way tougher with a mouse, and other stuff, such as pressure sensitivity on brushes, that is simply impossible on a mouse or trackball. Also, the tablet is much more intuitive to just pick up and use. It feels more natural being able to move your hand to where it belongs on the work surface, than to move your hand and wait for feedback from the cursor on your screen to know you did something right.