In my opinion, formal umpire training can be divided into three tiers:
Tier One: Professional Umpire School
There are only two professional umpire schools that are recognized by the PBUC:
The Jim Evans Academy of Professional Umpiring
The Harry Wendelstedt School for Umpires
Tier Two: The "Highly Regarded" Clinics and Camps
These camps are strictly developmental.
MLB Umpire Camp
The Southern and International Umpire Camps
Jim Evans 5 day clinics
Tier Three: Regional Training
Generally hosted over two to three days, the goal of these camps is to fine-tune skills and identify regional umpires for college level games.
Arizon Umpire Training
Bruce Doane Sr. Umpire Camp
Mid American Advanced Umpire Clinic
Tier Four: All other clinics
Generally these are local association hosted clinics that last a day or two. The goal of these clinics is to develop local umpires.
I will try to add to this list as camps/clinics open.