I made a website that finds where to buy tracks from DJ tracklists. Had to wait a couple of months for it's first £1 as I had no efficient way to drive traffic to is (the CPA from PPC was way too steep). It makes a few quid a month and pays for itself. Funnily enough it generates affiliate commission from Amazon, and that pays for the hosting on EC2...
I attended the Hacker News meetup tonight at SkillsMatter, London. A couple of the talks were really striking and I took away one main point which was about marketing from day one. Most of the stuff I've done has involved forums and I generally get accused of spamming.
Please take a look at the site, it finds where to buy dance music from DJ tracklists/charts.