Cyber Dimensions....

Here's a list of Official Google accounts on Twitter:

twitter.com/Google - our central account
twitter.com/Blogger - for Blogger fans
twitter.com/GoogleCalendar - user tips & updates
twitter.com/GoogleImages - news, tips, tricks on our visual image search
twitter.com/GoogleNews - latest headlines via Google News
twitter.com/GoogleReader - from our feed reader team
twitter.com/iGoogle - news & notes from Google's personalized homepage
twitter.com/GoogleStudents - news of interest to students using Google
twitter.com/YouTube - for YouTube fans
twitter.com/YouTubeES - en Espanol
twitter.com/GoogleAtWork - solutions for IT and workplace productivity

Full list @ Google Blogs.