PhotProc is an open-source photo editing program for Symbian, currently designed especially the PureView 808. The 808 has such a good camera, that it deserves good photo-editing on the phone that takes advantage of the high quality of the images from the camera.
PhotProc can do some quite advanced photo-editing directly on the phone, such as:
PhotProc can process photos up to the full resolution of the PureView 808 (38MP) directly on the phone. It has a background "job queue", which it processes while letting you edit a new photo. It processes preview images as you edit, including letting you zoom in and out.
Here is a guide by someone using PhotProc: http://www.hdrfotos.nl/pureview/?page_id=499 This is currently from a slightly older version of PhotProc, so the interface is a little different, but the advice is still good.
What PhotProc can't (currently) do (hey, it's open-source, feel free to add your own features!)
PhotProc for developers: [PhotProcDevel]
The wiki uses Markdown syntax.
Wiki: Correct colours in lighting
Wiki: Dynamic range
Wiki: Emphasizing colours
Wiki: Reduce noise
Wiki: Resize and crop
Wiki: Shadows and highlights