Ask HN: Resources for acquiring customers?

Hi HN, I'm looking for good resources (books, links, services, advice, etc) on acquiring customers. We all know that even with an exceptional product and a market that wants it, sometimes its hard to get people/companies to fork over cash. Lists of services you use to manage customer acquisition would be great, as well as anything you've found that works particularly great (Adsense -vs- Facebook ads, etc). Thanks!