Mediagoblin has monthly project meetings. One of the things I wanted to automate was meeting reminders that gets sent x days in advance, contain the link to the Meetings page in the wiki, and specify the date and time of the next meeting. I figure if we automate it, it's one less thing we have to think about---it just happens.
To do this, I decided to write phil. For the most part, it's sort of a throw-away project, but it was so small that I decided to go through a complete project development cycle with it and make sure it had all the bits a mature Python project should have: proper packaging, license, configuration, tests, project infrastructure, ...
I think it took about 10 hours over the course of 2 weeks. I was learning the icalendar library and python-dateutil and also figuring out exactly what I wanted it to do as I went along. For a small project like this, that's fine. For a larger project, I'd prefer to spend more time researching and designing ahead of time.
It was nice to "take a vacation" and put all the other projects I normally work on on hold to throw something together from scratch.