When the Posterous blogging platform was acquired by Twitter back in March, its users were told that a tool to export all of their posts was coming "in the coming weeks." Well, the day is here, and the backup tool is now available on Posterous’s site. The news was originally reported by The Next Web. Using the tool, Posterous users will be able to grab an email link to a .zip file containing the HTML for all of their posts, as well as all the photos and videos they've uploaded over the years. There’s still no word on how long Twitter is planning to keep the service running — the company said its purchase was an acquihire — but we’ll keep you posted.