@Chirag_Mehta mentioned a service called Gumroad to me. I tried it out and it is pretty cool. The designer of Gumroad gets it. If people are following you on Twitter, they already see value in what you share. So there is no need to market to them the traditional way. All Gumroad needs to provide is a simple friction-less transaction for sellers and buyers of small digital goods such as pieces of source code, a photograph, or a small piece of digital art.
If you have a piece of digital content that you think might be useful for others, go ahead and sell it. I will pay if I find it useful. So will others. The possibilities are endless. You may have a good PowerPoint template for presentations, an illustration that you created for a demo, an excel macro you put together to calculate something, an icon you created for an app, a photo you took, a research article you wrote about a topic, an industry or a company.
Here is an intro to Gumroad.