Mirv Jumping:

Introduction
Mirv jumping is very useful. Although it is probably one of the most difficult things to be able to pull of with a high chance of success. Why? Because it needs perfect timing. A grenade timer is almost vital to mirv jumping, in my opinion. Download some mirv jumping demos:

2Fort5 / 2Fort5R Mirv Jumps (2 demos, zipped)
(26 KB / Very small )
(note: It is in QuakeWorld Demo Format)