Where I'm from, we have a city league (no USTA affiliation). We play three times a week. Two of those occasions are doubles, and the other is singles. Doubles and Singles each has it's own Rankings/Ladder.
For doubles, players are divided into groups of four going down the rankings based on who shows up for that night. Three sets are played, and you change partners after each set so that after three sets you have partnered with everyone in your group. Based on the number of games won, the rankings are refigured in some way that basically makes it so the top player of the group gets bumped to the next highest group for the next session and the player with the worst results gets bumped down the next lowest group.
Singles works basically like a singles ladder, and matches are determined by who shows up for each session.
It's great practice, and good to know that you'll always have a good match at least three times a week. Play continues all year, and we only miss days due to rain or snow. Usually, as long as the weather is clear and the temp is at least 30 F there are plenty of players that show up.