Plugins - Flux Validator (form validation)
Add to favoritesFlux Validator is a handy, Ajax based form validation plugin for Rails.
The Flux Validator auto-magically validates forms against their models
and displays a list of error messages for each invalid field, all without
a page refresh.

I can't get the AJAX-part of this this plugin to work. I use rails edge and latest versions of all dependency JS-libraries. Plus, if I enable my AJAX date-selector I get "too much recursion" if Flux Validator is active - not otherwise.