Arch Linux -- This is the distribution of Linux that I have been running for years. This distro is what you make of it, and does require either familiarity with Linux or a willingness to learn Linux.

Blender 3D -- THE 3D software package I use for all my 3D art. It's wonderful, powerful and FREE. Though I own a seat of Lightwave, I've given Microsoft windows the boot so I don't use LW any more. (I still have an install on a machine or two so I can enjoy some of out favorite games in MS, but we also play many of the FPS games Linux offers as well.)

Inkscape -- Inkscape is a free vector graphics package. I've used it to do a few things and enjoy using the package. The BigPony logo on this website was done with Inkscape, for example.

GIMP -- This is the workhorse image manipulation and creation tool I use for raster images. I have done a few quick command-line things with ImageMagick as well (the thumbnail images for the Hair Particles presentation is an example of using ImageMagick.