The ASP.NET group at Microsoft released the Atlas Control Toolkit this week.  If you’re doing ASP.NET stuff, you’ll want to look at this.  They’ve got quite a few built-in Atlas controls.  Scott Guthrie sums it up on his blog.

It is the start of what is going to be a very large set of controls that make common Ajax scenarios super easy.  Want to add nested drop-downlists to your page?  Use the new CascadingDropDownList extender.  Want in-line popup support within a page? Use the new PopupControl.  Want to implement smooth show/hide support?  Use the new Collapsable Panel.  Want to add water-marking support to input controls?  Use the new TextBoxWaterMark extender.  All of these controls can be used on a page without having to write any code or custom JavaScript, and have Visual Web Developer and Visual Studio toolbox and WYSIWYG support built-in.