What tools and policies do you use to manage and maintain your mailing lists?
All of the mailing lists that I send e-mail to are powered by vBulletin, so really my only job is to make sure that spammers are not registering, I only send e-mail to the forum members who have asked for it, and do disable future e-mails to members who have addresses that generated any flavor of 5xx permanent error code.
I have a few ezmlm lists in various qmails. There is a listserv hosted by a provider of mine for my paintball team, and my own forum does lists too, but i don't really use it much (phpbb . net). On a side note, since upgrading last year to phpbb3 a few days after it came out, I haven't had a single spammer join my team's paintball forum.