The market for Android applications is growing enormously. Not only, but mainly in the official Android Market thousands of apps are available. Hundreds of new Android devices get activated daily, and where massive amounts of potential consumers are, many people want to get into that market. Android is based on Linux and uses Java as main programming language. You have basic Java knowledge and are a enthusiastic Android user? You probably want to lean how to make Android applications! 

There are hundreds of tutorials, guides and stuff out there but Google already provides you with maybe the best: the Notepad tutorial. You only need some components:

1. the Android SDK
2. Eclipse with the ADT plugin
3.  the official Android tutorials
4. Enthusiasm

With all that you might be soon earning some extra cash from your own applications.