I'm middle-aged and with a chronic illness so my social life has definitely cooled down as of late, but depending on my mood and "battery charge" I like eg. just going for walks with friends (with their dog if they have one!) in a nature preserve that's pretty close by to where I live. Often we'll have a joint and/or a couple of beers with us and we'll just sit on a rock in the middle of the woods, ramble and get a wee bit fucked up (but not too much).
I also really like going to gigs, me and a couple of my friends go see some local bands about once a month or even more often if I'm feeling up to it, it's a nice way to spend the evening – start off at a friend's place, shoot the shit for a few hours and have a beer or two, then head over to the venue.
Board games are also fun. Used to play Unsettled pretty regularly with a couple of friends but we haven't done it for a few months because I've been a bit low energy