IRC channels to join;
#suddendeath (Sudden death official IRC-channel, pretty busy and popular)
#quakeworld (official quakeworld IRC)
#qwrookie (probably the most busy channel, very good to be in, you also get +o to be able to use the serveme bots)
There are of course more channels, every clan has a channel of their own, most often every tournament as well and so on...
Quakeworld.nu is the most important site of all!
To find games, there are good serverbrowsers all over the place;
of course you have the built-in client serverbrowser which works perfectly well.
You also have
http://www.quakeservers.net/quakeworld/servers/pl=1/so=8/ where you can see basically all servers and what players/spectators are on them.
Or you could just use the QTV site, from which you can connect to the QTV of servers and spectate games, or simply copy the server IP and join the server from the client. This is the one I use personally and it works great for me. The URL is http://qtv.quakeworld.nu/.
DreamHack winter is nice, but make sure to show up to the quakeworld lan "QHLan" which is hosted once a year, most often in Stockholm, Sweden.
If you have any more questions, feel free to ask, and welcome to QuakeWorld!
Yours,
Andeh