Not sure if this is the right category as there is no Tools Showcase. Here is something I have been working on for a few weeks to help rapidly prototype a wide variety of textures. The emphasis is on simplicity over power but you can still generate some pretty cool looking images. Click to run:
http://www.angryoctopus.co.nz/colourspace/screen_1.png
Controls are pretty basic, just drag a block into the schematic, right click for properties.
The blocks are very simple to code and I can think of many more I could add (Blur, Tileify, etc.), will possibly integrate Beanshell for custom blocks. The great thing about this is the library is less than 100k but can generate huge detailed textures quickly so could really help reduce distribution sizes (once I get save/load xml sorted).
Here is an example texture that took approximately 1 minute and 5 blocks to make: