Is there an official place to see what they are up to or is the torrent sites the easiest way to find out?
The only official place is the Microsoft website where you wont be kept up to date on the latest builds. The only news there will probably be when the final build is up for technet.
And you have found the easiest way to find out, this site
Just keep an eye on the 'News' and 'General Discussion' pages and look for a new build number every once and a while