I think species identification using keys in books and compendiums is rather ineffective because you always have to look up the next step and associated pictures on different pages. So I was wondering if there are any simple and free tools to digitize the key? At each step you choose the best fit between two descriptions, and I would like to have both text and pictures (interactive if possible) in the description. I've seen some local botanical keys that filter results based on answers to short questions, but that's not really what I'm looking for. It should ideally be possible to start the key on any taxonomic level. Any ideas?