Highly Customizable Form Validation With jQuery.validVal
jQuery.validVal is plugin for the popular JS framework which aims to simplify form validation.
It can be used for validating any kind of HTML form (including Ajaxed ones) and works by defining the rules within class names.
There are 3 default validations included ("required", "numeric" and "email-format") and new ones can be included by defining new regular expressions.
A very nice built-in invalid handler helps calling-to-action on invalid fields and its behaviours can be quickly changed or improved.