Ask HN: How do you advertise to potential customers?

I've been doing a lot of research on customer acquisition and how companies are using social media as a way of handling potential inbound marketing. Also, how these online methods of advertising are lowering the cost of customer acquisition.

I've spoken to all of the people that I know, in person, that work at large, non-technical companies about how they generate leads and stuff. Most of them pay big bucks for pre-compiled lists of potential leads that have been collected by other marketing agencies, for them.

As a web-based company, what tools or strategies do you use to advertise to potential customers? I ask because I'm not familiar with most of the options, I'm sure. I only really know of the common AdWords.