Training Hundreds of Users in Many Different Sites?

A Very Anonymous Coward asks: "I work as a technical writer for a web-based, highly secure, collaborative software program. My company has been growing at a huge rate and we now are faced with the task of training 300+ new users at 80 different sites across the country. We can travel to the sites but this is costly and our human resources are fixed so we want to avoid this. My question is what is the best way to do this type of large-scale training, especially when it is not possible to get everyone together in one room?"

I already have a comprehensive help system (created with WebHelp from Ehelp.com) complete with a "How to" section. I am thinking of creating a "Product University", a modular set of documentation where each module teaches about a different area of our product. Ideally, this material would be multimedia rather than text based. I have used a great product by Qarbon.com and it will probably play a good part of this multimedia help. This material would be the same as what we currently provide in live trainings but would be made available online 24/7. We have in the past and want to continue using WebEx for some training. We have found that the ideal size of a WebEx training is 4-5 people. Are there any alternatives to training large numbers in a group?"