At last month’s North Shore Web Geek Meetup, I met Gal Arav, the creator of Newsflashr (and formerly creator of InstantBull):
Newsflashr aggregates feeds from a large number of news sources, and lets you scan the headlines from those feeds as a tag cloud (what are the interesting terms which appear frequently in the headlines in those feeds) as well as in a list sorted by Alexa rank.
It’s the kind of site you can spend a lot of time in, if you’re a news junkie, playing around with different sorting options and looking for trends in the data.
Here’s the tag cloud, for example of the “elections 08″ topic as I am writing this post:

Check out Tweet Clouds - new app which uses the Twitter API to create a tag cloud based on your tweets, optionally suppressing @s and removing stop words.
Here’s mine (click to see full size):
I wonder how much this changes over time, or how far back they are able to grab tweets.