perlineditor
Interactively create textures with Perlin noise
...You can change the noise parameters, and you can edit the palette, either loading it from a gif, or using the palette editor (right click to open the color picker, left click to move the two selection points about). There's also a handy tool for tuning the palette as the image adjusts (drag on the red circle to adjust, the black circles to move the edit range).