PhotoGraff was a pet project I worked on over one of my work terms that was due to all the hype on Hacker News on HTML5 and specifically the canvas element.
Prior to this, I didn’t have significant JavaScript development and I really felt that it was a good precursor to my enjoyment of building web applications.
Here’s a screenshot:

In terms of coding it out, the main challenge was just figuring out how all those pieces fit in together and fitting components in to modules. For example, if things like Backbone.js had existed, it would have been easier to force a specific method of piecing together components in the application such as the paint tools, image editing settings, etc etc.
At the moment, the app is down and I don’t plan on working on it anymore. Therefore I’ll try and get around to cleaning up the application and perhaps making it open source on my Github.