ImageNet provides a large image database organized according to the WordNet hierarchy in which each node of the hierarchy is depicted by hundreds and thousands of images. Currently an average of over five hundred images per node are available. You can download preprocessed features, bounding boxes or attributes even the images are available these are for noncommercial use only though.
Libccv is an open source image classifier and computer vision library.
It runs on Mac OSX, Linux, FreeBSD, Windows, iPhone, iPad, Android, Raspberry Pi. In fact, anything that has a proper C compiler probably can run ccv. The majority (with notable exception of convolutional networks, which requires a BLAS library) of ccv will just work with no compilation flags or dependencies.
Among lots of other things it has a SIFT implementation
The sources are available on github.