.htaccess, YSlow, and "Use cookie-free domains"

Is it possible to use .htaccess to redirect all requests for a particular folder on www.example.com to a folder on static.example.com instead?

Possible, but counter productive — the client would have to make an HTTP request, get the redirect response, then make another HTTP request.

This costs a lot more than the single line of cookie data saved!

Would this method also fool the CMS into thinking the images were located in the default locations on its own domain?

No.

Although this is easy to do, I would lose the handy ability within my content management system (Joomla/WordPress) to easily reference and link to these images.

What you could try to do is create a plugin in Joomla that dinamically creates these references.

For example, you have a plugin that when you enter {dinamic_path path} in an article, it appends 'static.example.com/images' to the path provided. So, everytime you need to change the server path, you just change in the plugin. For the links that are already in the database, you can try to use phpMyAdmin to change them in this structure.

It still loses the WYSIWYG hability in TinyMCE, but is an alternative.

In theory you could create a virtual domain that points directly to the images folder, such as images.example.com. Then in your CMS (hopefully at the theme layer) you could replace any paths that point to the images folder with an absolute path to the subdomain.