Notes I wrote up months ago that have since been found by others to be useful. Posting for posterity. Basically, these instructions are for how to set up an always-on logger for IRC (chat) - helpful for being able to hear the conversations others are having about the project you're working on while you're away. I am assuming a fair amount of background knowledge here, but the content is remixable, so feel free to yoink/improve/etc.
1. ssh into the box you have an account on - for instance, Sugar Labs folks can use sunjammer (aka people.sugarlabs.org) by requesting an account at http://wiki.sugarlabs.org/go/Sysadmin/Shell_account_request
2. Run these commands (comments in parentheses).
(a dialog will pop up, hit return to kill it)
(you'll get a mostly blank screen, with a stripe across the bottom with the
time and a number  in brackets - that's the window list - and then a line
below that with [(status)] in it, which is the description of the window that
you're in, and the place you type the rest of the commands.)
(and then, if you want, /msg nickserv identify <password> to sign in.)
/set autolog on
(it'll start storing things in ~/irclogs in self-explanatory filenames)
(and whatever other channels you may want to be in)
(You'll notice that every channel you join opens up another window - the first
channel will be in window 2, the next in window 3, and so forth. Use ctrl-p
(previous) and ctrl-n (next) to switch between windows, or alt-NUMBER to jump
to the NUMBERth window.)
(You'll also notice that the numbers for each window light up in different
colors when someone joins/leaves a channel (blue), talks in a channel (white),
or calls your name in a channel (pink).)
(All the normal IRC commands work as expected, and so does tab-completion.)
(a note on /whois: if you have a PM window open for that person, the whois
information will appear in the PM window. Otherwise, it will appear in window
3. When you want to stop, do
/away <away message>
and then detatch from screen, which is
(ctrl-a followed by d)
which will dump you in your normal sunjammer shell outside of screen.
Or you can just kill the terminal by typing
When you log in again, restart the screen session with
...and you'll be back. If you then type
...you'll see all the messages sent to your nick in the meantime in window 1,
and you'll be set to not-away.
I mostly find irssi useful for being always-on all the time and having backlogs
of conversations that have happened while I'm away. It also means that anywhere
I have ssh, I have IRC.