Zergling rush
 

This is the worst thing I know! It COMPLETELY ruins the game if someone does this. Does anyone know a good strategy to avoid getting killed from a Zerg rush with terran or protoss?

Strategy
 

The only thing I know to do is build up marines and set up a barrior.

If you are quick enough with toss get about 5-6 cannons up...that will stop 12 lings in their tracks.

Ans--

5-6 cannons? That would be slightly impossible against a zerglish rush, since there isn't that much time, unless they search every base spot on a 256x256 map and "finding" you last.

Cannons stop anything that requires a range of 1 attack.

I mean look at thier attack, they hit you from 0 to attack you.

Assuming they attack with 6 zerglings, I'll make up a quick strategy.

1. Playing as Terran - You probably wont have enough time to make a refinery, and thus firebats, so you'll have to rely on marines.

http://www.ancientcurse.com/terran.jpg

One well placed bunker with 3-4 marines and a SCV repairing it will be fine.

2. Playing as Zerg - You have a choice here, either buildings or units. I personally prefer using sunken colonies. While your spawning pool is being built (Slow!) make two creeps, and as soon as that pool is done, make them into sunkens. Might as well make two zerglings while you're at it.

http://www.ancientcurse.com/zerg.jpg

Or, you can ignore the creep completely and just make 6-8 lings.

3. Playing as Protoss - The most difficult, because it takes years to make everything. Your best choice is to make a gateway, and 2 or 3 zealots. One zealot can handle 2 lings. If you have time, make a forge and thus a cannon quickly near your nexus.

http://www.ancientcurse.com/protoss.jpg

Nice tutorial.
Either way, it's still a problem to avoid a good "rusher", since he can avoid the immobile defense systems in most cases. 2-3 Zealots don't help terribly much either, but the bunker will most likely do the trick.

Zealot are fantastic I tell you and can handle at least 3 each, and if they are together u can kill 5-6 zerglings easy without loosing more than 1 Zealot