<p>I know about using a -vsdoc.js file for <a href="http://en.wikipedia.org/wiki/IntelliSense" rel="nofollow noreferrer">IntelliSense</a>, and the one for jQuery is easy to find. What other JavaScript, Ajax, and DHTML libraries have them and where can  I find those files? Also, is there a document which outlines the specifications for -vsdoc.js files?</p>

An excellent blog posting from Betrand LeRoy on IntelliSense format for JavaScript:
The format for JavaScript doc comments
.
In a nutshell:
Summary - used to describe a function/method or event. Syntax:
```
```
<summary locid="descriptionID">Description</summary>
```
```
Parameter - describe a parameter to a function/method. Syntax:
```
```
<param name="parameterName"
    mayBeNull="true|false" optional="true|false"
    type="ParameterType" parameterArray="true|false"
    integer="true|false" domElement="true|false"
    elementType="ArrayElementType" elementInteger="true|false"
    elementDomElement="true|false"
    elementMayBeNull="true|false">Description</param>
```
```
The param tag is used to describe the parameters of a method or constructor. The param tags should be in the same order as the method or constructor's parameters and have the same names.
Function return type - syntax:
```
```
<returns
    type="ValueType" integer="true|false" domElement="true|false"
    mayBeNull="true|false" elementType="ArrayElementType"
    elementInteger="true|false" elementDomElement="true|false"
    elementMayBeNull="true|false">Description</returns>
```
```
Value type - describes a property (shouldnt use 'summary' for a prop) - syntax:
```
```
<value
    type="ValueType" integer="true|false" domElement="true|false"
    mayBeNull="true|false" elementType="ArrayElementType"
    elementInteger="true|false" elementDomElement="true|false"
    elementMayBeNull="true|false"
    locid="descriptionID">Description</value>
```
```
Field - used to describe a field in a JavaScript class - syntax:
```
```
<field name="fieldName" type="FieldType"
    integer="true|false" domElement="true|false" mayBeNull="true|false"
    elementType="ArrayElementType" elementInteger="true|false"
    elementDomElement="true|false" elementMayBeNull="true|false"
    locid="descriptionID">Description</field>
```
```
How to include IntelliSense for an external JavaScript file, the following syntax as the first line(s) in a JavaScript file:
```
```
<reference path="path/to/the/script/reference.js"
    assembly="Assembly.Name" name="ScriptResourceName.js"/>
```
```