For Unix/C:

lsys: L-systems as PostScript (in C++)

ftp://ftp.cs.unc.edu/pub/users/leech/lsys.tar.gz

lyapunov: PGM Lyapunov exponent images

ftp://ftp.uu.net/usenet/comp.sources.misc/volume23/lyapunov/

SPD: fractal mountain, tree, recursive tetrahedron

ftp://ftp.povray.org/pub/povray/spd/

Fractal Studio: Mandelbrot set; handles distributed computing

ftp://archive.cs.umbc.edu/pub/peter/fractal-studio

fanal: analysis of fractal dimension for Linux by Jürgen Dollinger

ftp://ftp.uni-stuttgart.de/pub/systems/linux/local/math/fanal-01b.tar.gz

XaoS, by Jan Hubicka, fast portable real-time interactive fractal zoomer. supports X11 (8,15,16,24,31-bit colour, StaticGray, StaticColor), Curses, Linux/SVGAlib

http://www.paru.cas.cz/~hubicka/XaoS/