VINCO Online Games:the best site to play at! Nice interface,
clocks, saved games, bots, tournaments, and friendly sysops.
Yahoo! Games: Very good site. Features ratings, timed games, and you can always find someone to play with. Requires Java-enabled brower.
PlaySite/Lycos Games: Good site. Nice interface, but sometimes slow. Offers ratings, timed games and daily tournaments, but sometimes it is difficult to find an opponent. Requires Java-enabled browser.
Internet Othello Server (IOS): The mother of them all. This is the first virtual othello gameroom on the net and you can find many world class players and computers here. If you are not a big fan of UNIX like text interface, several programs provide you with nice graphical user interface. You can also use IOS Java Client, or download Macbeth.
MSN Gaming Zone (formerly Internet Gaming Zone): As with anything from Microsoft, you get lots of clueless players, minimal functionality, and it only works in Internet Explorer (now you can download a plug-in for Netscape, but then it only works for Windows version of Netscape).