I am always astonished by this, too. Finding housing and finding a job both seem like problems that are really ripe for some sort of optimizing solution. It's an incredible amount of work for the people on both ends of the process — renters and landlords; employers and would-be employees — because there is so much information to sort through, in a plethora of non-standard formats. Looking through listings (or piles of applications) is truly the lowest common denominator.
Anyway, if you're not aware, Craigslist has a "Housing Wanted" section: http://sfbay.craigslist.org/hsw/ (for the Bay Area)
Also, although this is not what you asked for, http://www.padmapper.com does make searching through listings a lot less painful.