OP here. My question was not so much about finding collaborators for my specific projects, but rather to find a website where people shared theirs. The examples

OP here. My question was not so much about finding collaborators for my specific projects, but rather to find a website where people shared theirs. The examples I gave are just the kind of projects I'd like to find in such a site. The points you raised (what to get out of the project, communication methods, time investment...) is the kind of information that would fit in the "Description" section. Ideally (for me) would be a site you browse, find a project that catch your eye (big data? deep learning? bioinformatics? etc.) and you jump in, contributing what you believe you can (and learning in the way). No long term plan, just plain old hacking.