In my most recent role, I've contributed significant code to the Yocto project. Yocto project tools are used by a range of companies (Wind River, Intel, MontaVista, Freescale, Texas Instruments) to build embedded Linux distributions.
The autodividers widget for jQuery Mobile. I was pleased with this as it was a commit to a large public project which (at the time) was used by a lot of people.
I contributed a few commits to Intel AppFramework, a kind of jQuery equivalent. I was pleased with this because I was accepted as a maintainer of the project very soon after contributing to it.
I added SPARQL output support to Tracker. I'm proud of this one because it's C code, and therefore one of the most technically-challenging things I've done.
I wrote a description of different rotation types for the Clutter cookbook. I was pleased with this one because I think I captured some quite difficult concepts in a natural, easy-to-remember way ("wheel", "letter box", "door").
Slider Puzzle; requires Chrome or very recent Firefox (tested on 22.0b3). Unlikely to work properly on mobile or iOS.
NB the app is intended to be used from a local filesystem: over the web, the images take a while to load but there are no progress indicators, so please be patient.
Also NB if your brower's locale is set to Finland, the text should appear in Finnish.
This uses the excellent bops library, which provides a facsimile of node's built in buffer operations for use in the browser. It's used to read the binary data from the .mobi file.
es-media-player: A very simple long-format mp3 player. The key reason I wrote it was to track progress through multiple podcasts, and keep track of what you listened to last so you can pick it up again. Similar to what the Audible apps do, but for your own mp3s, and with a very basic interface designed to be used by thumbs.
I explain it in more detail in this blog post.
There's also a README in the application code which may be of interest.
The name is as bland as possible to avoid any copyright infringement (my initials). Though there is an ES file browser, so I might have to change it to something else. It was originally called Marconi.