This week Twitter announced that all public Tweets are now indexed and searchable back to 2006. Until now, searching on Twitter's interface returned recent results from within about the last week, but searching for older Tweets required using a third-party service, such as Topsy. While third-party services are still helpful tools for searching deleted Tweets and other advanced analyses, this is a welcome addition to Twitter's use as a research tool. Read more in this excellent article in Wired, and more about the technical details behind the index on Twitter's Engineering Blog.