Graph The classic network-mapping applet from Sun Microsystems. An applet to rotate .obj files in 3 dimensions. MouseTrack Try to catch the box with your mouse. An applet to rotate .xyz molecule files in 3 dimensions. A good learning applet.
Simple code makes some unique animation.
Blink Make your text flash with different colors. The classic game with a surprisingly apt opponent. NervousText Make your text dance. Animator A simple sequential animator with background sound. About as basic an applet you could imagine.