I thought it'd be fun to try building a hack with the new API, so I made a simple visualization of your entire Twitter archives in ThinkUp — ThinkBack, a ThinkUp-powered time capsule. Take a look at my history, or on the @whitehouse account to get the gist.
ThinkBack analyzes your entire Twitter history, extracts entities from the text, and colors them based on category. Grouped by month, it also gives you a quick glimpse at your posting activity over time.
For the entity extraction, I used an excellent free web service called AlchemyAPI to extract people, places, events, product names and other keywords from everything I've ever posted. They provide a category for each, which I assigned a color.
I also tested two other free web services that offer entity extraction, text-processing.com and Zemanta. Finding and categorizing keywords from short status updates is no small feat, but AlchemyAPI does a remarkable job. (If you'd like to play around with all three, support for both Zemanta and text-processing.com is commented out in the source code, but easily swappable with AlchemyAPI.)
ThinkBack also uses four typefaces from Google Web Fonts, my first time using them and dead simple to implement. For free fonts, the quality's surprisingly great, with several faces commissioned by Google itself. For a quick, free hack, it's a great alternative to Typekit.
I also used a very simple PHP templating language called RainTPL, which I chose as a lightweight alternative to Smarty. In practice, I found it too simple. Its handling of complex data structures and loops required me to jump through hoops that shouldn't be necessary. (I'll stick with Smarty next time.)
Anyway, you can download the code here, it only requires PHP and access to a recent version of ThinkUp. Feel free to fork it and submit a pull request for anything you add!