Desk Calendar is a small application that, cleverly enough, puts a desk calendar in your browser. It shows the months as a desk or wall calendar would, allowing navigation from month to month.
While providing real functionality, it's primary purpose is to act as a self-tutorial and test bed of some modern web development technologies.
I chose a desk calendar for a few reasons. For one, I'm fascinated by time and dates and calendars. Also, it's a nice simple problem domain that I understand well. At the same time, it presents some interesting implementation challenges.