How to create applications that look right, behave properly, and fit into the GNOME user interface as a whole, covers specific advice on making effective use of interface elements, and the philosophy and general design principles behind GNOME interface.
By Evan Miller. essay about how you can get paid to write great open-source software. If you're not a software developer, you should probably spend the next few minutes of your leisure time on a web page other than this one.