Mechanical Turk: Amazon's Mechanical Turk is a resource for doing human-intelligence tasks, or as the site commonly refers to them, HITs. You get paid a very small fee for any given HIT and you'll need a good deal of volume to make a substantial amount of money. But it is a resource you can use in your spare time to generate a small income online.
Don't sacrifice morals for a quick buck — At the outset, you'll want to do all sorts of things to make money online, but don't sacrifice your morals for a quick buck. Not only will you put people off, but you'll lose Google's trust. You also shouldn't concern yourself with things like Adsense or other ads on a blog before you have around 100,000 visitors per day. Yes, per day.
Write pitches. If you have located a client for whom you want to write, send pitches, which are topic ideas for articles. Write pitches that not only show your expertise, but also demonstrate your enthusiasm for the topic. First, read the publication to which you are sending pitches to familiarize yourself with what they publish. If applicable, identify a specific section and send our pitch to the appropriate editor. Also, include a brief summary of who you are.