I know there are a lot of generators for fractals like the mandelbrot set or julia sets for android already, but all of them were missing out some nice features in my opinion. Therefore I created a new (free, code available) application called FractView: https://play.google.com/store/apps/details?id=at.fractview
It has some really nice features:
* You can enter your own formula. For the mandelbrot you simply enter "sqr z + c", a nice phoenix set "sqr z + re p + z1 im p"; z(0) = "c", z(1) = "c" and p = "0.56667,-0.5". Also I implemented symbolic derivation which makes it very easy to view newton sets: "newton(sinh z + c)" looks really amazing. There is also support for nova-fractals in a similar way.
* You can edit the color palettes (there are two: One for divergent points "bailout" and one for non-divergent points "lake"). For colorization I use cubic spline interpolation in the L*a*b-color model.
* Very intuitive multitouch support for up to 3 fingers. Basically, whenever you drag on the screen with a finger, you drag the pixel right below it (a bit like super-fluid cookie dough). With two fingers you get arbitrary scaling and rotation, with three fingers you can also shear the image, which is in particular nice for fractals like burning ship ("sqr cabs z + c") or tricorn ("sqr conj z + c").
* You can save images of arbitrary size as PNGs, share them instantly or set them as wallpaper.
* You can bookmark your favorite places.
* Images are rendered from the center and with increasing resolution, so you get an instant preview of the fractal.
* Values are cached so that changing the color does not require rerendering the whole image. Also, values can be normalized in the range of values.