Java Applets differ from JavaScript in that you have another file, (sometimes two,) called a class file to upload to your server and onto your webpage directory on your hard drive.
The advantage is there is a lot less space on your webpage. You can use one file of special effects commands for more than one webpage.
The list of links on my Seasons page are called a syndication. They have an applet on their server. I have a short JavaScript on that webpage that links to their applet.
The guestbook and counter on my home-page works the same way.
Java Boutique had a few background scripts that I used on my Easter section.
The LVHues script on my Good Friday page changes color through a mask made with a second graphic. On my resurrection page you can see the effects of the same applet without a mask.
Code Brain is another excellent resource. The Code Brain Yak Kit script on my Holy Saturday page has multiple possibilities. I used it for a six graphic mouseover.