America's Job Bank:
www.ajb.dni.us
Every interview I've gotten has come off that board. Every other site just gave a lot of listings that let me feel productive but didn't actually accomplish anything. I like monster too. However, don't use the Apply Now button. Look for an e-mail address and use that instead.
Personally, I hate Flipdog. Sometimes I go to read the listings and the job on the website isn't actually in my city. I have also never gotten a response from any company I've seen listed there.