Ask HN: Best resources to learn + implement online marketing plan?

I have a web-based application that I've been developing over the past year. It was originally developed for a client's own use with an agreement that I'd be able to re-sell it as a generic solution. Since it went live, I've received a few new clients just through word-of-mouth from other organizations that have seen it and want something similar. In my (admittedly small) sample of 10 organizations I've talked to in my local area, they have all reacted positively to the app, and 4 have actually paid money for their own instance so there appears to be a real market for it. For the implementation/sales process think of it as a BaseCamp-type site where most of the customers would be paying extra for a custom skin, though there are some pre-built skins that would allow for instant setup & use.

I need to develop and implement a marketing plan to actually get this launched as a business, but I haven't a clue how best to go about it. I understand the basics of SEO, search advertising, email marketing, A/B testing and analytics but am looking for a guide on how to put it all together. Can you recommend any good books that layout the basics of the various online marketing activities, gives real-world advice on what works best for which goal, what order to do them in and how to maximize the return on time and money?

Thanks