Virtual Mailing List Managers?

stan7826 asks: "I'm the sysadmin for the USGS Earthquake Hazards Program here in Southern California, and we currently run a small set of public mailing lists for earthquake information. We currently have a set of five lists. Two for long messages, two for short pager-style messages, and one for an ASCII-art map of earthquake shaking. People can subscribe to the list they want from our web page. But we are now looking at making this a statewide service, with a sort of cafeteria-style interface. We want for people to be able to select what events they get notified for by region, magnitude and message type. If I just create a mailing list for each combination, I get 24 different lists for California. This is just begging for some sort of database-driven virtual mailing list manager. Does anyone know of such a beast? (Preferably open-source, of course!)"