Kayaking with friends
I go kayaking on Tuesdays, Thursdays and most weekends. It's brilliant during the week, after work, to completely unwind. A group of us paddle out on the local lake and usually bring a flask and treats.
There's something about being out on the water that's great for relaxation, but to be honest it's as much about the social aspect as it is about kayaking...being out with like minded friends, being close to nature and having a good cuppa and a chat.
Can't recommend it highly enough.