We've spent 0 so far, and have had pretty good results. The blog is huge, and I started the company blog almost six months BEFORE launch. I'm also active in the general tech community and try and leave meaningful comments on the blogs that matter to what we're trying to do. And it has paid dividends. We're still in private alpha, but will be opening up our doors in 2 weeks.

Then its SEO, SEO and more SEO.