The ASP.NET AJAX Control Toolkit is a classic set of ASP.NET WebForms extensions that helps you build ASN.NET websites. Now maintained by devexpress.com

rich set of helpers used to build highly responsive ajax-enabled Web applications. These helpers include the Grid, AjaxDropdown, PopupForm, Lookup and more

Silverlight Toolkit and Silverlight for Windows Phone Toolkit are a set of Microsoft components for developers.