在ASP.NET AJAX官方网站上有如下三个下载：
1．ASP.NET AJAX：这部分是ASP.NET AJAX的核心部分，包括了核心AJAX类型系统，网络协议层(networking stack)，组件模型，扩展器(extender)基类，以及与ASP.NET集成的服务器端功能(包括广受欢迎的ScriptManager，UpdatePanel，和 Timer控件)。功能列表如下：
服务端功能列表
Asynchronous client-to-server networking
Authentication as a Web service
ControlExtender class
Profile as a Web service
ScriptManager and ScriptManagerProxy controls
Static page methods as Web services
Timer control
UpdatePanel control
UpdateProgress control
客户端功能列表
Authentication for JavaScript
Behavior class
Calling .asmx Web services from JavaScript
Component class
Control class
Debug class
JavaScript Array type extensions
JavaScript Boolean type extensions
JavaScript Error type extensions
JavaScript Number type extensions
JavaScript Object type extensions
JavaScript String type extensions
JSON serialization
Profile for JavaScript
Trace class
2．ASP.NET AJAX “Value-Add”CTP：ASP.NET AJAX社区支持的“增值”CTP部分，包括了以前各个Atlas CTP版本包含的，但并不在完全支持的“核心”1.0 版本内的额外的高级特性。通过进一步的反馈，这些将会逐步稳定的增加到核心1.0中去。功能列表如下：
服务端功能列表
AutoCompleteExtender class
Cross-browser Web Parts drag-and-drop
DragOverlayExtender control
PopupExtender class
客户端功能列表
Actions components
AutoCompleteBehavior class
BatchResponse class
Binding component
Button control
Checkbox control
Click behavior
Counter class
Cross-browser Web Parts
Data control
DragDropList control
DragDropManager component
DraggableListItem control
FadeAnimation component
Floating behavior
Hover behavior
Hyperlink control
Image control
Input control
Label control
Layout behavior
Opacity behavior
Popup behavior
Selector control
ServiceMethodRequest class
Sys.Data and Sys.UI.Data namespaces
Textbox control
Timer control
Validator controls
xml-script support
3．ASP.NET AJAX Control Toolkit：包含了基于ASP.NET AJAX 1.0 版“核心”下载版本的28个非常酷的免费AJAX控件。它是一个开源项目，由微软和非微软开发人员共同开发的，去CodePlex下载代码。
二．安装ASP.NET AJAX
1．在安装ASP.NET AJAX 1.0 Beta之前，需要先卸载以前所有的CTP版本。
2．下载ASP.NET AJAX 1.0 Beta安装包，安装时Microsoft.Web.Extensions.dll程序集将被安装在GAC（Global Assembly Cache）中，所以使用时不需要再在Web站点的Bin文件夹中包括该程序集。
3．下载安装ASP.NET AJAX “Value-Add”CTP和ASP.NET AJAX Control Toolkit。列表如下：
名称
描述
Accordion:
Create efficient UI from multiple panes with this animated control.
AlwaysVisibleControl
Docks a panel to a corner of the browser window and keeps it visible even when the user scrolls.
Animation
Adds powerful, easy to use animations to any element or control.
CascadingDropDown
Easily link drop downs, complete with asynchronous population and no postbacks!
CollapsiblePanel
This extender allows panels on your page to collapse and expand with no code.
ConfirmButton
This extender adds a confirm dialog to any Button, LinkButton, or ImageButton control.
DragPanel
Makes any panel into an object that you can drag around the page.
DropDown
This extender can wrap any control to provide a SharePoint-style drop-down menu that is attached to the control.
DropShadow
This extender adds attractive drop shadows to any control on the page
DynamicPopulate
Replace the contents of a page element with the result of a web-service call.
FilteredTextBox
Restrict the types of input that text boxes will accept.
HoverMenu
Allows UI to pop up next to a control when the mouse hovers over it.
ModalPopup
Allows you to show styled modal UI without using HTML dialogs.
MutuallyExlcusiveCheckBox
By adding a number of checkboxes to the same “Key”, only one checkbox with the specified key can be checked at a time.
NoBot
Applies simple rules to prevent automated bots or scripts from posting to a page.
NumericUpDown
Allow users to easily increase and decrease values using the mouse to scroll through values.
PagingBulletedList
Add paging and sorting to long bulleted lists.
PasswordStrength
Give your users visual cues to help them create secure passwords.
PopupControl
This extender turns any panel into a popup.
Rating
Let your users easily give feedback by rating content with this easy-to-use control.
ReorderList
This control is a full-featured data-bound control that allows its elements to be reordered on the client via drag and drop.
ResizableControl
Allow users to dynamically resize content, right in the browser
RoundedCorners
Rounds the corners of any control for a clean, professional look!
Slider
Adds an elegant scrollbar-like user interface for setting numeric values.
TextBoxWatermark
This extender adds "watermark" prompt text to TextBoxes on the page.
ToggleButton
This extender turns an ASP.NET CheckBox into an image checkbox.
UpdatePanelAnimation
Animates page elements corresponding to hidden postback activity.
ValidatorCallout
This extender enhances the functionality of existing ASP.NET validators.
三．在Visual Studio.NET 2005开发基于ASP.NET AJAX的应用
安装完ASP.NET AJAX后，打开Visual Studio.NET 2005中新建Web Site，在项目模板中会出现一项ASP.NET AJAX-enabled Web site，直接选择它就可以了，如下图：
新建完成的项目中会自动在Web.config中做好相关的配置，并且AJAXExtensionToolbox.dll已经添加到了VS的工具箱中，不需要再手工添加。
概述篇简单的介绍这里，从下一篇开始学习ASP.NET AJAX中的每一项具体的功能。
下篇预告：ASP.NET AJAX入门系列（2）：使用ScriptManager