How to control the blinking of keyboard leds.

Nothing irritates you more than blinking keyboard leds while you are working on your computer. They generally intimates you about your num lock or caps Lock key, if ON. Keyboard leds can definitely be used for other meaningful purposes also.
The keyboard leds can be controlled by a device driver called the misc driver. That driver can control all kinds of misc things. You could write your own driver to make them blink or light up at any system event.
A program called tleds is available from http://www.hut.fi/~jlohikos/tleds.html. That program will have them blink based on network usage. This will lead to blinking of one LED for incoming packet and one for outgoing packet.