First of all, yeah I definitely second Rob's suggestion about using Twitter. The #phdchat hashtag is a good one, and I've also seen #researchjobs, #phdjobs, #academia, etc. and of course just #phd is a big one too. Then there is the hashtag or popular search term for any given academic conference (e.g. #ASA2012 in my field, or currently just 'AES conference' for the one in NY right now, etc.).
And there are also some relevant tweeters you might dry getting to retweet you directly (e.g. @GradHacker, @InsideHigherEd @chronicle, @hapsci, @wheStudent, to name a few I'm familiar with, you could probably find more). Twitter is no panacea, but it's increasingly popular with doctoral students and young academics and is effectively "ground-up" as you say.
Along these lines there are also some very popular blogs (e.g. http://www.gradhacker.org/, or specific to sociology orgtheory.net ), though you have to be more delicate about how you promote your project there - though you can always just send the writers an email about it and see if they'll do it for you. And certainly a lot of almost-done phd students I know surf the Inside Higher Ed, Chronicle, and Time Higher Ed websites.
As for listserves, I only know only of small departmentally-run ones for their own students on the market like we have here at UChicago, or very subject-specific ones (ComUrb and UrbGeog are popular with urban studies people) that are only partially about things like job announcements and contain a large number of current faculty, emeriti, and early-stage grad students and undergrads who would not be particularly interested. Others may know of something better.
Finally, while I'm sure you've thought of this and know that 'offline' fora are less ideal for what you're talking about (unlike online, there is no single giant room where everyone considering academic careers is hanging out waiting to hear from you), one semi-ground-up example I can think of from my own recent experience would be just attending something like a 'Preparing Future Faculty' workshop that many universities' careers/guidance offices put on. I attended a 'future faculty luncheon' at UChicago the other day that was focused on teaching at liberal arts colleges, and basically they had like twelve phd students in there and a handful of profs from nearby colleges talking about their experiences, recruiting, etc. and it was very casual. It sounds like you work for a group that might do similar stuff at Northwestern so I'm sure you know all about it... but basically getting either yourself or at least your literature to those sorts of things might feel a little more grass roots than just blasting an email out to everyone on your (or some other university's) list. The same can be done at conferences, where many almost-on-the-market students are often browsing job fares and departmental functions, etc.
Hope this helps! Sounds like a worthy cause you're working on in a tough market!