There are a number of avenues to go for hiring, like LinkedIn, traditional Craigslist, Monster listings, etc.
I personally use Startuply.com (YC '08) for a lot of the hiring that I do. It's proven to be pretty good in terms of volume as well as quality, but you have to be pretty patient.
Where do you find candidates for hiring for job openings?
EDIT: Apart from networking. That's obviously the top for both quality and quantity.