These are things Janice Harper has written about mobbing. I bought this book on amazon, it has gotten me through the last few months at work:

I will try to put up a blog entry here or on another site (I will update with a link) summarizing the strategies you're supposed to take.

This is a podcast that could also be helpful:

This woman has become my personal hero. Understanding what goes on with the people around me when they become collectivelly aggresive has helped me over time become more stable and hopeful about my situation.