They're still in business?! In the late 90s, I would wheedle a few bucks out of mom every two weeks to get a few rounds of combat in Duelmasters. It was a surprisingly rich simulation. The game was obviously pay-to-play in the most direct way possible, so my gladiatorial team never advanced to much of anywhere, but waiting for the biweekly printouts was still a huge thrill. The operators even facilitated passing hand-written notes between players as an anonymous mail system!
The other, older, founding operator of PBM games is the wonderfully named Flying Buffalo, Inc., who are also the publishers of Tunnels & Trolls.
I used to play a lot of Daifen [1], a French play-by-mail game that blends strategy, diplomacy and role play. Games can last about a month, with different game speeds (one turn per day, three turns per week, etc.) It's still up, though the player count isn't what it used to be. You can do everything in the interface, from sending orders to planning battles to contacting other players, but the core mechanic of play-by-mail is still there. I sometimes toy with the idea of making an international version...
I made a comment somewhere, where someone was asking about FTP games, and I thought there were looking for games that would be like this. You'd upload stuff to an FTP server instead of mailing it...
Play-by-mail games are a pivotal part of John Darnielle's novel WOLF in WHITE VAN. Some of these games sound like ones depicted in the book. Very interesting!
The PBeM server on gamerz.net has a good sized list of games they host. http://www.gamerz.net/pbmserv/ (I used to play a bit of Firetop Mountain long ago - http://www.gamerz.net/~fm/ ). Note that this is a very old server and I haven't checked if anything is still running.
COLLECTOR - Not only do you enter modded Breyers in online horse shows, you even have your R card. Next up: scratch build.
ENTREPRENEUR - Thanks to optimising tax breaks (and a partner from a good family with a day job), you live up to the title of the book Losing Less Money Raising Horses.
COMPETITOR - You marry your vet. This just makes it official, the two of you already spent nearly all your waking hours together anyway.
SOCIALIZER - You wish to make friends so you can collectively flame the benighted heathens who use a different colour tack or prefer a different breed.
The other, older, founding operator of PBM games is the wonderfully named Flying Buffalo, Inc., who are also the publishers of Tunnels & Trolls.