Maggie:
Charlie has provided some really good resources for you to take a look at. I would also suggest a book by Mark R. Edwards and Ann J. Ewen entitled, "360 Feedback". The book is a bit technical but it does provide some good insight. Personnel Decisions Incorporated has an excellent book out entitled, "The Successful Managers Handbook". The book does not get into 360 in particular but it would be an excellent resource for the action-planning phase of the process.
If you are interested in viewing some 360 surveys I would be happy to send you (with permission) a variety of instruments that I have developed. I would also be happy to send you our impact study entitled, "The impact of feedback and follow-up on leadership effectiveness" and "The impact of feedback and follow-up on customer satisfaction". Let me know what your pleasure is and I will do what I can to be helpful.
When you are ready, I would be happy to provide you with some suggestions for scoring vendors to analyze the 360 data and prepare the feedback reports.
I have worked in the area of leadership development for many years and develop 360 surveys for many of the world's leading organizations. If you would find it useful, I would be happy to spend a few moments talking with you buy phone. Simply send me an email at alyssa@executivecoaching.com with your phone number and some good times to call and I will follow-up.
Good luck on your 360 journey!