Instructions for how to get going are available here:
http://bazaar.launchpad.net/~walles/foton/trunk/annotate/head%3A/README.txt

Foton has a UI that can view photos. The UI can be zoomed and window resizes are handled. Images can be rotated and deleted.

Double clicking an image will bring it up full screen, go back with ESC.

The --import-from option allows photos to be imported from a camera.

Features that has code + tests but no UI:
* Create and edit tags. Tags can have other tags as parents.
* Apply tags to and remove them from photos.
* Search for photos by tag(s).

Bonus items that can wait until after the first release:
* Full screen slide show.
* Zoom (scroll wheel) and pan (move mouse) in full screen mode.
* Improve zoom slider performance. Removing all images from the table and putting them back again is really slow.
* Metadata in Adobe's XMP format.
* Support for EXIF-based JPEG rotation without depending on external program exiftrans.
* In full screen mode, cache one image in each direction so that arrow-key image switches are faster.

Done:
* Display photos in a window.
* Zoom the viewed photos using a slider that determines how many photos should be displayed on each row.
* Resize photos to fit window when window is resized.
* Show photo metadata; ISO, resolution, flash, shutter time.
* Render visible photos as good as possible before rendering not-visible photos.
* Rotate JPEGs by changing the EXIF tag only.
* Rotate photos.
* Support (read & write) for the Freedesktop Thumbnails specification at http://jens.triq.net/thumbnail-spec/introduction.html
* UI for setting photo directory.
* Import photos from a camera, without importing duplicates.
* Sort photos by shooting time.
* Delete images as described here: http://www.ramendik.ru/docs/trashspec.html
* The importer does not re-import deleted pictures.
* Double click an image to zoom in on that image.
* Delete and rotate images in full screen mode.
* Arrow keys should change picture in full screen mode.
* Context menu in full screen mode for rotation, (un)deletion, exiting full screen and changing images.
* Improve cold start (empty disk cache) performance.

To get involved, make a branch and e-mail me patches! Fixing small things you find annoying is a good way to get started! Unit tests are run by invoking src/test/runTests.rb, they must pass before anything goes in.