5 Roach rush

Build Order

9 Overlord
13 Spawning Pool
13 Extractor
15 Overlord
Zergling
Queen
Drone
Drone
Roach Warren (latest you should start is when queen is 70% done)
Zergling speed when you have 100 gas
Drone
Overlord when queen pops, inject larvae
Drone
Take drones off gas once you have 125
Re-inject
5 Roaches (Warren, OL, and injection should all pop very close to each other)
Overlord (31/34 food)
Drone
Expansion when your roaches are walking to the enemy
Re-inject
Zerglings as you get the minerals, rallied to your opponent's base
Queen

Basicly a strategy to play offensive and defensive at the same time.

More info in this thread: Teamliquid Forums