We use irc.freenode.net/#chromium for technical discussion as well as communicating about the current state of the tree. For user questions, visit the unofficial support channel at irc.freenode.net/#chromium-support.
An unofficial IRC log seems to be hosted at http://echelog.matzon.dk/logs/browse/chromium/. It's likely that anything you say here will be copied in triplicate forever, so only say things your mother would approve of or you wouldn't mind being on the news.
If you are contributing or wish to do so, it is a good idea to connect to this channel. In particular, if you are committing, please connect to the channel so that the sheriff or others may notify you of build breaks and other time-sensitive issues with the build infrastructure. Consider adding your IRC nick to the table here: http://code.google.com/p/chromium/wiki/UserHandleMapping, espeically if it varies wildly from your @chromium.org account name. (This helps us know who to ping when things go wrong.)
To find out whether your mapping is working (or to find out who to yell at if you're a sheriff), you can ask trungl-bot who a user is:
nick#chromium> trungl-bot: whois user
and trungl-bot should respond shortly with an answer like:
nick#chromium> nick: It looks like user could be: email@example.com / :da_nick / firstname.lastname@example.org.
You can also do this sneakily in a private message with:
/msg trungl-bot whois user
trungl-bot is a helpful automated servant who can answer many questions for you in the channel. Find out what it can do by asking for help, er, "halp":
/msg trungl-bot halp
For example, find the current sheriffs using:
/msg trungl-bot sheriffs
Getting op permissions for #chromium via chanserv
If people in the channel repeatedly get off topic and are making it hard for sheriffs or chromium contributors to talk without distractions, it may be suitable to give them a ban with timeout.
You must first be identified (chanserv requires this) and have the correct permissions. Ask someone who already has privileges with chanserv (anyone who gets an automatic +v when joining) to grant you the appropriate flags. They will need to run:
/msg chanserv flags #chromium <your_nick> +ARVfiorstv
on your behalf. You should know this is successful if you are given voice automatically on joining #chromium. If there are problems just ask on IRC (and if no one responds, start with maruel@, thakis@, or awong@).
Off-topic folks in the channel
If you already have permissions with chanserv, to give an off-topic nick an hour to file a bug, gather repro steps/screenshots/test cases, and otherwise see some sunlight, use:
/msg chanserv akick #chromium add <their_nick> !T 1h [optional rationale that's logged with chanserv]
If you'd rather do this manually, you can op yourself as follows:
/msg chanserv op #chromium <your_nick>
and kick the user with something like:
/kick #chromium <nick_to_kick> [optional rationale for kicking user]
and if you'd like to un-op yourself after:
/mode #chromium -o <your_nick>