ItsYourTurn.com (IYT) is a turn-based game server including Go, Go-Moku, Havannah, Chess, Chinese Chess, and other games. Based upon web browser access. Time limits are from 3 days per move to 45 days per move, but allow no byo-yomi.
Nodog: When I played there (about a year ago now), the scoring on the go games was horrendous. The players would have to score the games themselves to figure out who actually won, but the IYT server kept record according to its terrible scoring algorithm. For turn based games, I much prefer DragonGoServer.
Andreas Teckentrup: One of the disadvantages of the server is that it lacks a ranking system, but the ladders and the regular tournaments are quite nice. Non-Members only have up to 15 moves per day and can only play in one ladder.
Xue: (posted dec. 2008)I've been playing there for about a year now, since 2007, and it seems like they've fixed the scoring system, I haven't had any problems with it. I can confirm the lack of a ranking system, due to which your opponents level will be...very inconsistent. I only play Ladder, and after the first couple games, everyone tends to be pretty good.