egroups
It's worth taking this opportunity to mention egroups. In the past mailing lists required contacting each individual group to subscribe, and if you wanted to unsubscribe the process was usually a pain. egroups allows you to subscribe to a wide range of lists with ease. It gives you an opportunity to either receive the individual messages, receive a daily digest, or read the messages online. There is also a strict anti-spam policy in operation. Old messages are archived (which adds to the wealth of information available) and the various groups have space for storing files, running polls, etc.. Most lists are open to everyone, but some lists have restricted membership, and it is even possible to set up private lists which are not displayed in the egroups directory. So go ahead, visit the egroups site and register, then spend a bit of time searching the large range of mailing lists available.
Recommended mailing lists
One of the best available is WABlist - a mailing list for Warhammer Ancient Battles. The list advertises itself as "set up for players of the game to swap ideas, tactics, battle reports, ancient military history, miniature collecting and painting tips and generally have fun". They have succeeded at all of these. In the last couple of weeks: army lists were devised and discussed, historical questions debated, miniatures reviewed and much fun had. The absence of several regulars (away at Historicon) gave rise to a great deal of humour - though the list seems to be fairly relaxed at all times!
Second on my list of recommendations is ColonialWars. This has a web page run by Tim Peterson who also has the excellent unofficial Foundry site. I'm not sure, however, that TP will appreciate my publicity for this listing since he recently made the following comment on the mailing list:"Geez, were you guys handing out the address at Historicon?". This listing is devoted to warfare in the 1800's with the particular emphasis: "sources, terrain making methods, miniatures, and rules will be common, as will discussions of games played and scenarios...". The tone is slightly more serious, as perhaps you would expect from a bunch of old Victorians, but no less instructive and enjoyable than that of the WABlist. (There seems to be some cross-pollination between the two.) The listing has a "restricted membership" which means the moderator of the ColonialWars group has to approve your request for membership.
