The NECC DVD can be purchased here - The New England Catching Camp - Online Store
The Wasserman High Level throwing e-book can be purchased here - High Level Throwing: Baseball Edition E-Book – $50.00
The Kobota defensive drills DVD here - DVD’s | Softball Skills.com
^^^ This ^^^
And has been said by others: have a plan in place, and practice to the plan. Set time limits for any drill or skill development, and only deviate if they show proficiency in the skill early (IOW, it's ok to cut a drill short if they're all doing it well and correctly; but don't extend the drill, just hold it again the next day). It is far too easy to get bogged down on a single skill. Discuss it, demonstrate it, have them practice it, then move on.
Each skill taught should build on previously taught material, so look to create progressive practice plans.