Online venues that promote networking among scholars -- alternatives to Academia.edu and ResearchGate Are there alternatives to Academia.edu and ResearchGate if one is searching for a venue that promotes "informal" (*) cooperation and networking among scholars (specifically, in mathematics and science)?

(*)  As far as I know, the aim of two sites mentioned above is mostly sharing papers rather than opinions, insights, and interesting material of various sorts related to research. I would like this alternative site to be more informal: a scholarly social network rather a mere preprints repository.
Have you tried linkedIn? They have tons of mathematics groups on there you just have to use the search bar. Or have you tried joining a meetup group? You can go to www.meetup.com and find groups of you interest that are near you area. It is not solely online but it is a great way to meet different people who have the same interests as you.