Since you compared with yahoo and craigslist, then your next level would be a PR 8 site. To achieve that, you should be considering placement in high PR directories so you can begin accumulating thousands of backlinks. An Alexa rank of 329393 for a three month site is impressive.
I did try submitting to different social bookmarking services. I did get some clicks out of it. But not constant. Along with that I took an extra step developing and offering some free tools. - link popularity and alexa rank checker - bookmark tool I had quite a few visitors using the tool thus getting free advertisement from it. I agree with craigslist guy. Getting a higher PR. I have PR 3 right now. It may go little up when google updates ranking next time.