Those of you who are already LJ volunteers or staff of one stripe or another can tune this out.
LiveJournal does a lot with volunteer labor. This is because it is not run by a huge corporation, unlike some sites. Six Apart is pretty tiny, and it can only devote one slice of effort to LJ. Also, having users of the site help out with it makes, in the end, for a superior service. It's my belief that part of the reason that LJ has the community feel that it does is that it relies on people like you to help out.
Yeeessss, people like you. I think you see where I'm going here.
LJ could use people. Lots of people, doing lots of different things. If LJ has meant something to your life, if it's helped you in some way, this is a great way to help it in return. (And maybe get something for yourself out of it, but let's not dwell on that.)
The simplest way to be an LJ volunteer is to do Support. There's no application process and the barrier to entry is insanely low. Do you know how to update your journal, friends-lock entries, and read FAQs? Yes? Then you have something to contribute in Support if you really want to. It's easy to get started, too - anybody can leave screened answers on the support board, and the user won't see them until they're looked over by a senior volunteer. If you're interested in Support, hit up the Support Guide and try it out. You'll be glad you did! (Well, I'll be glad you did.)
If you want to help improve LJ's documentation, look into the lj_userdoc community; you can go there and post suggestions, which will be reviewed and acted on by senior volunteers and staff.
Or maybe you'd prefer working on LJ's schools directory. Well, there's a volunteers group for that, too! Check out the user profile of lj_schools for information.
If you speak another language, you can help translate the site into it! Information on how to participate in that may be found here: http://www.livejournal.com/translate/.
And, last but not least, if you can deal with the worst LJ has to offer, check out the LJ Abuse Team. Information on how to apply may be found in the profile of the lj_abuse community.
If you have any questions about any of these groups, please go right ahead and ask. I'd be happy to talk with you about how they work.
I was part of LiveJournal support for several years. It's a nice community (and a way to meet and make new friends, if you want), and it can be very gratifying knowing you've helped someone. It can also look good on a résumé later on, especially if you get more experience and end up being able to train support volunteers newer than you or possibly even being administrator of one of support's categories.
And as tamar offered, if you're interested in helping out in any way or if you'd like to have more information about something that is described here, then please comment on this entry. If I don't know the answer to your question myself, I will find it out for you.