I've written a simple fractal program as a hobby project, and I'm releasing it as freeware. The program is called "Janus Fractal", and it lets you create Iterated Function System fractals and manipulate them interactively. It uses a texture feedback algorithm: each frame, it renders the fractal to a bitmap image in memory, and then the next frame it uses a copy of the previous frame as input for that one, scaling it down, applying rotations and other transformations and so on. It's all done with software rendering, no 3D hardware acceleration for the time being.
There are 6 fractal types implemented: Julia fractals (these are not IFS fractals, but you can render them with texture feedback, so I threw them in), Tree fractals, Spirals, "n-around-1" fractals, L- Systems and 3D IFS fractals.
You can load various pre-made fractals using "File->Quick Load Fractal", then use a combo-box and slider bar to edit fractal parameters, or drag blue "hotpoints" around to edit the fractal interactively. The type of fractal is selected from the "Transform (X)" menu and the various components of the fractal motif are selected from "Generator (Y)". Rendering options (colouring, blur, HDR etc) are in the Options menu. Help -> Show Keymappings shows keyboard shortcuts.
There is an HTML manual that comes with it that you can pull up from the Help menu (or open it from the Manual folder).
Here are some links to download it (for Windows only at the moment):
Janus Fractal v1.111 (.rar file): http://www.megaupload.com/?d=SU2HM0QQ
Janus Fractal v1.111 (.zip file): http://www.megaupload.com/?d=WX2NLNXV
This is the first release, at some point in the future I hope to add more features like zooming, more flexible L-System specification and so on.