This may be more accurately phrased as how to survive using legally free software...

Browser: Mozilla Firefox

Newsgroup Reader: Mozilla Seamonkey

Vector Graphics: Inkscape

Image Converter: Squiggle, ImageMagick

LaTeX Editor: TeX Shop

Music: iTunes

DVD Ripper: HandBrake

Video Player: VLC

Generally Useful: Xcode, Image Capture (shift+command+4)

Again, this may be more useful to me than to others, but here is a quick and easy way to make circular level sets in matlab:

[x,y,z]=cylinder([1 0], 1000);
contour(x,y,z)
axis equal
axis image
axis off

Told you it was simple. The 1000 parameter is what makes the circles more circular and less octogonal. By default it's set to 20, which isn't so pretty.