Tweet Nest 

A really nice lightweight PHP app for archiving and browsing your Tweets on your own server. Installed it on my personal site in less than 5 minutes, then lost at least half an hour exploring the stuff I was tweeting about in 2009.

For example, here's how I reacted when Jeff Veen announced Typekit, long before I knew not to capitalize the 'K', and long long before I ever imagined I might work for them.