Over the course of beRecruited's growth, we've relied heavily on organic growth and grass-roots marketing. Similarly, we've used Elance, Craigslist, and Kijiji to outsource smaller projects... and, while each is time consuming, it's been effective for us on a project-by-project basis. Now we are hiring a full time beRecruited SportsWrap editor and a few bloggers and, while promoting the open role, I was quite disappointed to find that Valleywag's job board has closed! We had advertised on Valleywag previously and found it *far* more successful than any other medium. Not only were the leads plentiful... they were qualified! There are few locations to reach potential bloggers who are truly web savvy, get SEO, love sports, etc - but Valleywag worked.
LinkedIn works decently. Kijiji and Craigslist generate leads - but are time intensive (and Craigslist is expensive). Elance is better for projects and developments (rather than ongoing employment). TechCrunch, GigaOM, etc seem better for senior-level jobs than for recruiting writers.
Of course if you have any contacts or ideas - please pass my way!