Twitter recently posted its top trends of 2009, lists of popular words and phrases across several categories. The most popular topic across all categories was the Iran elections, followed by "swine flu" in the news category. It doesn't surprise me that Michael Jackson was the top-trending person of 2009, though I am surprised that Harry Potter beat New Moon and the most tweeted movie.
Twitter's full list of trends for 2009 is on its blog, including sports, technology, and TV shows. I enjoy looking at Twitter's trending topics from day to day, so I think this year-end retrospective is an interesting way to check out what the general tweeting population found interesting throughout the year.