GNU Photo Archiving software?

jonr asks: "After I got my Olympus E-100RS camera, I have been enjoying photography again. I now take on average dozens photos a day. Now the problem is ever growing photo collection. I found an excellent archiving software, IMatch but I'm looking for something similar to run under Linux. Folders and sub-folders are are just not cutting it. IMatch allows me to put my photos in a category tree, e.g. a photo of my dog could be placed in Family/Pets and Animals/Dogs. It also has off-line archiving, a must have for growing collection. Now does anybody know of a tool or a collection of tools for this?"