1. Advanced DHTML, Dynamic CSS
Chapters 17, 18

2. Animating an object
Take a look at script to move an object from corner to corner
You should have the basic idea from the tractor script shown earlier

3. Other actions Move in a circle Follow the pointer Draggable objects
Simple popup windows (this could be useful); these are also behaviors in Dreamweaver.
Move window
Resize it

4. Changing Styles
There is one example here in Chapter 18 that changes text size. Note
Object.style[stylename] = newVal
There is another in Chapter 24. You will need to adopt one or the other.
Other options here are reading styles from the sheet, and changing classes.
A more complete switcher changes the whole style sheet (also consider <link type="text/css" rel="alternate stylesheet" href="other.css"/> which still must be called in the page)

5. Using alternate stylesheets
Here's a script from alistapart.com that makes sure that other stylesheets are disabled, and that stores the style's status in a cookie
styleswitcher.js
Create alternate stylesheets with titles (no title for the original stylesheet)
<link rel="alternate stylesheet" title="fred" href="fred.css"/>
Connect to the script below the stylesheets
<script type="text/javascript" src="styleswitcher.js"></script>
Add event handlers
<a href="#" onclick="setActiveStyleSheet ('fred'); return false;">Choose Fred</a>
The original article is here.