My wife and I own an apartment building, and we had a vacancy come up last month. The wife put an ad in classifieds for the Register-Guard (Eugene, OR's primary newspaper). It cost something like $50-60 to run for two weekends, no weekdays. No calls.
I posted a free ad on Craigslist, and it generated 10 contacts, one of whom rented the unit.
Their interface may suck, but there's definately an active community.