IdealForms: a great new client-side validation framework
The boss pointed this one out to me. It’s a fully responsive JQuery framework for client-side form validation that looks better than most client/server validation! Quite an extensive (and extensible) array of form validation types/configurations are available out-of-the-box.
Note: it only supports IE from 8+, but you can search the issues list for ie7 and see his response to my posts about the one key problem with ie7.
View Demo here.
Edit: my needs were for a dynamic form (unknown questions called from a database) and this solution turned out to be a LOT of work to get it right. Still recommend for static web forms, though.