I found a very large collection of ASP.NET AJAX videos on MSDN that I thought that you might be interested in. There are about 60 of them! So, I will post them in 3 parts. Here are the links to Part 2 and Part 3.
Enjoy,
~Robert Shelton
↑ Grab this Headline Animator
#1 | How Do I:Get Started with ASP.NET AJAX?
7 minutes, 51 seconds
#2 | How Do I:Get Started with the ASP.NET AJAX Control Toolkit?
11 minutes, 15 seconds
#3 | How Do I:Use the ASP.NET AJAX CascadingDropDown Control Extender?
27 minutes, 56 seconds
#4 | How Do I:Dynamic Partial-Page Updates with ASP.NET AJAX?
12 minutes, 7 seconds
↑ Grab this Headline Animator
#5 | How Do I:Make Client-Side Network Callbacks with ASP.NET AJAX?
15 minutes, 26 seconds
#6 | How Do I: Add ASP.NET AJAX Features to an Existing Web Application?
7 minutes, 20 seconds
#7 | How Do I:ASP.NET AJAX Enable an Existing Web Service?
23 minutes, 31 seconds
#8 | How Do I:Use the ASP.NET AJAX TextBoxWatermark Control Extender?
6 minutes, 5 seconds
#9 | How Do I: Use the ASP.NET AJAX Popup Control Extender?
8 minutes, 51 seconds
↑ Grab this Headline Animator
#10 | How Do I: Use the ASP.NET AJAX ModalPopup Extender Control?
10 minutes, 29 seconds
#11 | How Do I: Use the ASP.NET AJAX AlwaysVisible Control Extender?
6 minutes, 17 seconds
#12 | How Do I: Use the ASP.NET AJAX Accordion Control?
9 minutes, 31 seconds
#13 | How Do I: Use the ASP.NET AJAX Client Library Controls?
10 minutes, 33 seconds
#14 | How Do I: Use the ASP.NET AJAX Collapsable Panel Extender?
11 minutes, 53 seconds
#15 | How Do I: Use the ASP.NET AJAX Draggable Panel Extender?
6 minutes, 16 seconds
#16 | How Do I: Use the ASP.NET AJAX DynamicPopulate Extender?
11 minutes, 19 seconds
↑ Grab this Headline Animator
#17 | How Do I: Use the ASP.NET AJAX FilteredTextbox Extender?
5 minutes, 30 seconds
#18 | How Do I: Use the ASP.NET AJAX HoverMenu Extender?
7 minutes, 41 seconds
#19 | How Do I: Use the ASP.NET AJAX ToggleButton Extender?
7 minutes, 57 seconds
#20 | How Do I: Use an ASP.NET AJAX ScriptManagerProxy?
8 minutes, 51 seconds