"Panel"
Downloads the HTML of a page into a text area.
Shows the use of

• Frames
• Buttons
• TextFields
• CardLayout
• WindowClose, Mouse, action events
• Threads
• URL handling
• Graphics
• Random

nb : the "save button" doesn't work. A "worm" appears if you click in the green area.

"Worms"
Worms creeping randomly. Some 10 more will hatch if you use your mouse ... (my wife does not like that applet very much)
Shows the use of

• Arrays
• Mouse events
• Threads
• Graphics
• Random

nb : I know this applet does not terminate very cleanly.

"FireWorks"
Reproducing fireworks in a frame. Very configurable... (speed, quantity/length of traces, random, gravity, friction ... try these other config :2, 3). My wife's favorite !
Shows the use of

• Frames
• Arrays
• Math class
• WindowClose, Mouse events
• Threads
• Parameters
• Graphics
• Random

nb : a quite clean code.