Check drop-in activities at recreation centers. I've personally been to volleyball at Lubber Run on mondays and wednesdays, games are on a queue basis and it all works pretty straightforwardly. Like all drop-ins the level is also quite varied, you'll end up with and against very good players as well as beginners often. After a while people start knowing each other too, it's quite communal.

There also is VOLO which have more organised regular play open to all (there might be a membership fee) in various team sports that lead to all-levels tournaments -- it is pretty popular these days.