This is a list of some other blogs that you might find interesting if you would like to read more about the Katamari Franchise.  Overall, there is no blog that constantly updates with new Katamari information other than the professional blog by IGN, and even that one is not updated frequently.  I did find some interesting posts though and I have listed them here:

Kellbot:  An interesting fan blog.  They chronicle their pursuit to make a real Katamari to play the game with.  Pretty intersting stuff!

Playstation.blog: This is a blog that talks about the new music for the new Katamari game that was just release in September, Katamari Forever.

Papercraft Army:  This is fun blog post (one that I have used!) to create your very own Katamari characters with papercraft!

Katamari Forever Blog:  The official IGN Katamari Forever Blog.  It does get updated, but not frequently.