I'd like to tout an increasingly rare hobby among younger people (non-retirees): Bridge, the card game. It has a rule structure and that hidden-information element that appeals to nerds, but it forces you to think critically and rationally instead of analytically (usually--opportunities for highly analytical plays pop up), and forces you to be able to relate with another person both at and away from the table, since it's played by pairs of 2. There's a reason it's Bill Gates' favorite game.
A lot of fascinating older people play the game, as well. I met a small business owner who was formerly the first computer salesman for a major mainframe company--IIRC it was Honeywell, but don't quote me on that. At least one famous international financier occasionally shows up to the bridge clubs in Chicago (unfortunately I've never ran into him).
The downside is it's hard to find a critical mass of bridge players in your age and "hang-out-ness" category.
A lot of fascinating older people play the game, as well. I met a small business owner who was formerly the first computer salesman for a major mainframe company--IIRC it was Honeywell, but don't quote me on that. At least one famous international financier occasionally shows up to the bridge clubs in Chicago (unfortunately I've never ran into him).
The downside is it's hard to find a critical mass of bridge players in your age and "hang-out-ness" category.