Yep, I make Chrome apps and extensions!
The developer account was incredibly cheap so I decided, why not? I think it lasts a lifetime because Google said on their developer registration page "pay a one-time fee of $5".
My best and personal favorite extension. A polar clock is a really awesome clock with bars that have different representations. The innermost bar is the month and the outermost bar is the seconds. They are colorful and animated, and are also pretty to look at.
- runs in a little popup next to the address bar
- customizable with options
- awesome demo video that explains everything on the Chrome Web Store page
- open source on GitHub (soon to be closed)