My experience has been that the huge Web sites (apartments.com, rent.com, etc.) will give you only a very small listing of what's available from only the most high-end/expensive places. I'd suggest something more local to your area if you can find it. Craig's List definitely if you have it, but see if the local paper has a listings thing online or if there's some local Web site that has listings for just your area.
For instance, in South Los Angeles we have southbayrentals.com When new hires come in for orientation at my workplace, they'll often group up and buy a one month subscription to split the cost.
Oh, and apartmentratings.com is great if you can find the place you're interested in it. Just be aware that most people go there to complain and some apartment rental places rate themselves (but are often easy to spot).
Two new apartments in a 9-month span for me last year.
Good luck.