To play NetHack on this server, just telnet to nethack.alt.org or use this Java or this Flash telnet applet.
Find many of us in #nethack on irc.freenode.org. (latest chatter) Our friendly bot Rodney announces all the embarrassing details of player deaths (and player achievements) in channel.
The game is vanilla NetHack version 3.4.3 with a few patches, and the options are set to NetHack defaults, but changeable with the 'Shift-O' option or in the nethackrc file, as always. Terminal options are finicky, but I find it best to turn on "color" and "DECgraphics" using most terminals that come with flavors of Linux. There is a little wrapper in place that will ask you for a login and password, and also allows registration and editing of custom options files.
The game has a couple options for showing running turn counts, point totals, and xp, as well as some coloring options for inventory and the hit point display. None of these should affect you if you don't want them.
Every game is recorded, and available for live viewing by all.
As of February 2010, this server is a virtual machine existing as an Amazon EC2 instance in the us-west-1a zone.