The slider will be included in the Control Toolkit
I'm pretty excited about it. The slider control evolved to a SliderExtender and seems ready to be shipped with the next release of the ASP.NET AJAX Control Toolkit. At the moment, you can find the slider extender together with a demo page and a suite of automated tests in one of the development releases.
Besides fixing bugs and issues, I worked on two main tasks: make Internet Explorer use the GenericDragDropManager instead of the IEDragDropManager (to avoid the drag and drop icons displayed by IE during a dnd operation) and provide a default layout for the slider to obtain a working slider with one line of declarative code.
I'm happy with the result, and the future improvements will be based on your feedback here or in the Control Toolkit forum. Also, I'm going to blog about the SliderExtender in detail when it will be officially released.
Finally, remember that if you coded a cool extender you can contribute to the Control Toolkit!