For marketing, I've found HARO (
http://www.helpareporter.com/) to be a really useful resource. Essentially, you have reporters who are looking for leads / sources, about a wide range of topics. Obviously, you're going to have a lot of "Jon & Kate + 8" and "fashion week" requests, but you occasionally get topics that deal with your area of expertise. You can then step in, and you get free exposure, in some fairly high-profile media outlets, and are quoted as an expert. Even the interviews that aren't in super-high-profile papers still give you a good chance to refine your pitch and to practice speaking to a non-technical reporter, so you've got a more polished presentation when it comes time to chat with the WSJ/NYT/etc.
So there's that.
BUT.
You might want to consider holding off on doing any publicity until, as zaidf mentions, you've ensured that you have a good product/market fit. In addition to Eric Ries and Sean Ellis, check out Steve Blank's stuff. If he were your advisor, and he heard you were looking to spend runway money on PR, he'd be apoplectic. He'd probably say that the best return on that money is going to come from doing user testing (that is, interviewing people to see if you have a product that they'd spend money on; if not, using the money to tweak the product, and then do another round of interviews; repeat), or from using it to extend your runway so you have longer to figure everything out before you run out of money.