Wow, that's an interesting model for revenue. I'm happy to see it's also a successful one.
I /intend/ to publish 10 posts about the project Euler ( cowbelljs.blogspot.com/2011/12/projecteuler-001.html ), step back and improve on them greatly, adding a lot more detail and clarity such that you could learn some algo/math from them and start offering them as ebooks. I'm not a fan of ads on the blog, simply because google forced them to be excessive and annoying with my template.