Imbo is an image "server" that can be used to add/get/delete images using a REST interface. There is also support for adding meta data to an image. The main idea behind Imbo is to have a place to store high quality original images and to use the REST interface to fetch variations of those images. Imbo will resize, rotate, crop (amongst other features) on the fly so you won't have to store all the different variations.
End-user docs can be found here.
Licensed under the MIT License.
If you have any questions feel free to join #imbo on the Freenode IRC network (chat.freenode.net), or ask them on the forum.