I have. Each series was as rewarding as the sum of its parts allowed it to be — usually for the better though not always adequate motivation to stick with it for long enough.
I think my favorite was a 4- or 5-race weekly (Wednesday evenings, IIRC) xc series in the fall (with a sibling series in the spring.) I believe it was sponsored by a local running store, $0 to enter, standings scored on cumulative time, each one was 5K-8K in a different park/location. This was in the middle of a sigificant metro area (4th largest city in the US) and drew some good competition.
I did enjoy an xc series that Wilson helped to cobble together before he fled to whiter pastures, though it was more of a regional competition and a bit far-flung plus the dates were seemingly rather randomly spaced. I think it may have been cancelled after its inaugural year (one or more of the events was cancelled) but was later revived. I believe the standings were scored on placement versus other series participants.
There is a local middle distance road race series (2K, 3K, 1 mile) in the town of 100K where I live, held on the 3rd Thursday of each month through the summer (June, July, August) and each is held in historic/shopping districts so that it is more like an evening outing for participant and spectator alike, with ample post-race feeding/drowning establishments nearby. This is typically a fun one, though the mile has been hampered by rain on occasion, and one that I enjoy volunteering for if not running in it. Standings in this one are also based on cumulative time.
There is also a local free xc series that alternates locations and distances (5.8K & 5K) on nearly every Saturday morning from September through May. Fun stuff, standings are scored by placement, though the depth of competition is often lacking and one of the alternating locations is unfortunately well out of town.