[bonniemuffin]

I was also thinking of Duolingo as a really successful example of this. My daily commitment is less than 5 minutes, but I often end up doing some extra once I get started.

Language learning is particularly good for the "little bit every day" method, because I find that I can only retain a little bit of new information in a single session (so there's no point in studying for an hour straight), but daily repetition really helps it sink into my long-term memory.