I like activities where you can show improvement, it requires your complete focus, you can do research on the side AND you can meet others. Hence why I have enjoyed crossfit.
Other ideas....cooking classes? You need to focus while doing it, can meet other people and can do research (read blogs, recipes, etc.) on the side. Also, you always can get better at it. Dance lessons could work as well, if you like dance. Same with martial arts.
I have been doing guitar lessons, which hits on all of the criteria except meeting people. I met my guitar teacher, but no one else. But it does require my concentration while doing it and I can do research on the side to take my mind off of things.
I also think a really good fiction novel can help. Something where you can get lost in the characters and story. You won't meet anyone reading but at least your mind is preoccupied.
Me: 40, W: 40 M: 15, T: 18 D - 10, S - 7 D announcement 6/7/2014 A discovered 7/20/2014 (but denied by W) Still living together and sharing same bed