Well Web 2.0 has finally wrapped up and during that time there are a few more APIs and examples that have come in. I'll do a wrapup post soon.
Zvents - A great way to find events. Some nifty APIs available. (Disclaimer - I am helping these guys out)
411Sync - An open API for SMS Search. This looks pretty cool.
eBayTime SMS - Mash up of eBay & 411Sync to get eBay Official Time
Rollyo - Social Custom search - Built on top of Yahoo search and also launched at Web 2.0 conference.