SnapTwitter is archive.org for twitter -- historical snapshots with a high degree of time precision. Be able to roll forward and backwards through time to see (and search) all of twitter at any point. Maybe it even has a visual timeline at the top of the page that lets you navigate through time. I'm up to my neck in my startup (see below), so I couldn't actually take on another project, but I thought I'd throw the id…
Out of all of the suggestions, I liked this one the most. jbr, give me an email to aupajo at gmail and it's all yours if you want it.