Oxidizer is a free open source fractal flame editor for the Apple Macintosh, running OSX 10.4 or greater.
Fractal flames take many shapes, here’s some crude examples made almost literally at random by Oxidizer. Only the colour scheme and the positioning have been altered.
Oxidizer
Nicer examples can found on the home page for the Electric Sheep screen saver with which Oxidizer shares a common code base. Both programs use the flam3 libraries to render the flames. This also means Oxidizer can read and write the flam3 file format used by Electric Sheep.
Oxidizer looks something like this...
