/r/ColumbusActive
/r/ColumbusSocial
/r/ColumbusMusic
/r/Riddeit (Columbus cycling sub)
and a bunch for electronic music production and DJing, as well as some music genres I especially like.
I highly recommend subscribing to your local subs if you have them. Mine are a great source for fun free stuff, such as the Monday Night bike ride x urban exploration get-together, some good local jazz nights, and (best of all) the opportunity to volunteer at the Columbus Beerfest. That was a good night.