In the fourth screencast in the series, Validation and Much More, I talk about how to add validation to your objects and how to show validation failures to the user. There's more on FormHelper and I introduce the PropertyBag and Flash. This is a consolidation episode, where I take the work we've done so far and fill in some of the common blanks. It's very much reliant on having seen the previous screencasts as I am using the same Visual Studio project throughout.
http://colinramsay.co.uk/screencasts/4/
One point of relevance: the use of ActiveRecord with Monorail is completely optional. I've used it here because I feel they integrate well, but if you've got another persistance framework which you'd prefer to use then that's possible too!
This screencast shows many of the small but very useful aspects of Monorail, and shows off the awesome binding abilities of FormHelper. For the next screencast I plan on taking a break from the normal series and into the Contrib project to talk about ActiveWriter and the CodeGenerator, projects which can make working with Monorail even easier!