I like both walking and running since it's basically the opposite of what I do in my daily live (sitting and thinking vs. moving and not thinking). It clears the mind in a sort of meditative way when you get your body moving, without thinking too hard about it.
On the other hand I got a great interest in the gastronomic world. Cooking and tasting food, beer and similar provides some possibilities that corresponds very well with my geekiness. There is a lot of different things that you can really dive into. There is a lot of interesting tastes and smells out there, and I find it really interesting to experiment with bringing them forward, and figuring out where they come from. Beer generally consists of 4 ingredients, the main one being water, but you can still make it taste pretty much like you want to.