Add this script to your page:

<a href="javascript:window.external.AddFavorite('http://www.yoursite.com/', 'My Site Title');">Bookmark This Site!</a> 

Change "http://www.yoursite.com/" to the URL you add the script to and 
change 'My Site Title' to the title you want to appear in their favorites.

Change "Bookmark This Site!" to whatever text you want to appear on the page.

That's all it takes folks. Best wishes.

The Little Guys