Zerg - general purpose build order

In this game I built drones until supply ran out, then a few zerglings to fend off scouts and scout themselves, and then Hydras. The Hydras fended off a nasty air attack on my drones, then shortly after that the tech finished to let my overlords drop them on my opponents' base, winning the game.

1:00:00 10/10 Overlord

2:09:00 14/18 Spawning Pool
2:26:00 14/18 Extractor
3:06:00 16/18 Extractor
3:50:00 18/18 Overlord
3:52:00 18/18 Lair
5:39:00 22/26 Hyrdralisk Den
5:43:00 Queen
6:33:00 24/26 Ventral Sacs Nasty 3 ship air attack kills off about half my drones right about here
8:34:00 ~10 Hydra Drop wins game

In this game I built drones like before, then a few creep crawlers, and made my extractors a bit sooner. I had resource shortage and overlord shortages. I also lost about 6 hydras to failed attacks against my opponent's expansion. With that, right after I left with a 12 hydra drop, my opp walked into my base and destroyed it. I should have brought the hydras back to defend, and they *might* have won the defense and been able to mount a counterattack. The counterattack was successful but I died before he did.

0:59:00 10/10 Overlord

1:51:00 13/18 Extractor
1:58:00 12/18 Extractor
2:24:00 13/18 Spawning Pool
3:33:00 17/18 Spine Crawler
3:39:00 17/18 Lair
4:18:00 18/18 Overlord
4:38:00 17/18 Spine Crawler
5:18:00 19/18 Hydralisk Den Scout overlord destroyed by sentry :(
5:48:00 Queen

In this game I went back to my first approach and tried to accelerate the hydra drop a little bit. I skipped zerglings, except for a scout pair, and cranked out 4 hydras before being torn up by a 10-zealot rush. More defenses required! I wonder if I can build the roaches faster than hydras? There were no resource problems this game.

0:57:00 10/10 Overlord

2:03:00 14/18 Spawning Pool
2:34:00 15/18 Extractor
2:50:00 15/18 Extractor
3:45:00 18/18 Lair
4:01:00 18/18 Overlord
4:13:00 18/18 Overlord
4:46:00 20/42 Zergling
5:11:00 20/42 Hydralisk Den
5:32:00 21/42 Evolution Chamber
5:35:00 Ventral Sacs

In this game I tried the same build again and was obliterated by a 6-pack of zerglings before I could build any units to defend myself. This was the other guy's build order.

1:10:00 7/10 Spawning Pool

1:32:00 8/10 Overlord
2:16:00 10/18 Zergling
2:16:00 12/18 Zergling
2:16:00 11/18 Zergling
2:31:00 14/18 Queen
3:07:00 17/18 Zergling
3:31:00 18/18 Zergling Death by Zergling around 3:20 (workers pulled off resources to defend, and killed in the process)
4:38:00 15/18 Zergling
4:38:00 16/18 Zergling
4:39:00 17/18 Zergling
4:39:00 18/18 Zergling
4:42:00 18/18 Overlord
5:42:00 21/26 Extractor
5:54:00 24/26 Zergling
5:54:00 23/26 Zergling
5:54:00 22/26 Zergling

Well, I'm thinking to myself that I don't want to start off every game with a 6-ling rush but I would like to be able to defend against it, and I do know I need some minor defenses at least to hold off the majority of super early game attacks.  I set a goal to have a "standard" build order that makes me capable of handily beating a 6-ling rush, just barely, with the best possible economy going on when the defense wins.  It's a small tradeoff to be protected in the early game and it doesn't gimp mid/long term game plans.  After a couple of 1v1 ai games watching the replays, here's what I come up with.
 
Decided to get a couple of zerglings and a crawler right around the time a quickie rush could hit me. Worst comes to, I can use the lings in my roach attack.


1:02:00 10/10 Overlord
1:32:00 10/18 Spawning Pool
2:48:00 17/18 Spine Crawler 12 seconds late, could have started 2:36!
Zerglings start coming out at 3:18, should be just fast enough to stop the early rush. Spine crawler done at 3:37 (17 seconds after rush could have arrived, need that 12 seconds)

After my first overlord, I shift gears and make a spawning pool instead of an 11th drone.  Immediately after the pool, I make a crawler, queen, and a pair or two of lings.  From there, I have typically been going roaches, but I think I need more info on what my opponent is doing to decide if it's worth that building or not.  If I execute everything quickly and efficiently, I should handily dispose of a 6-ling rush just as it's walking in my doorstep on a typical map.  If I'm not against zerg, I can perhaps have a good start at fending off a zealot rush or a reaper backdoor attack as well.