The best thing to blog about is blogging. You get a lot of income from it, and you also get to learn even more, from people's comments and suggestions they make. Blogging is always a great experience, you always learn something from your blogs. Specially the first ones, where you notice your mistakes and try to get better.
Like Darren Rowse, a highly respected full-time blogger, says: I blog about twitter and tweet about blogging. Sometimes I blog about tweeting about blogging and tweet about blogging about twitter.
