Twitshift – Follow Yourself on Twitter From a Year Ago
http://www.twitshift.com/

Twitshift is a service that lets you follow yourself on Twitter from a year ago. First things first — Sign in with Twitter to start importing your old Tweets. They will store your old posts on their server and repost them to a second account of your choosing on the same day you posted them last year. This will be added to Social Informatics Subject Tracer™.