One Hall Power to Keep/Stronghold
When it works
The build order
You now have 15 peons (11 on gold, and 4 on wood). You keep pumping out ogres from all 3 barracks as soon as your resources allow. You want to also have a peon chopping out, so that he is finished by the time you have 2 ogres finished. Just tell your first 2 ogres to stand ground in the space you chopped out, and no grunts will ever get through. You want to do this because if someone gets a catapult to your wallin before you are chopped out, they can contain you, and never let you get out. So you want to be able to get outside of your base as soon as possible.
As you get a few more ogres, send a couple around to scout. By the time you find the enemy, you should have 6-10 ogres and your cat. Send absolutely everything at them. You should easily take out any ground forces that they have. If they don't have a tower started or upgraded, they are already dead. If they do, use your cat to take it out. Make sure you don't lose any/many ogres to the enemies tower(s).
Alot of times the enemy will have a cannon tower upgraded in which he will repair with several peons against your catapult. If this is the case, then see if you can just use your catapult to attack ground in his peon line, in a spot that is out of range of his tower. On the maps that this strategy works on, you can do this alot of times, and win the game just by protecting your cat.
If you can't do that, just back up your catapult a little bit and start having at it, on whatever building you feel like. Keep pumping ogres non-stop at home, and sending them to the enemy. Because you did a peon stop (15 peons), you can just overwhelm the enemy off of your 1 mine. Just make sure that they didn't sneak out an expansion somewhere.
(2) On a smaller map where you know where the enemy is, or on a map with even smaller gold mines (one way in, one way out) even faster ogres are sometimes necessary. Follow the same order as above, but peon 2 only builds 4 farms (17 food total). You also don't upgrade any levels at your blacksmith until you are going stronghold. Start upgrading to Stronghold when you have 12 peons (yes 12!). Use your farm peon to start a second barracks, and start upgrading your first weapon at the smith. Two peons are used off of gold to build the mound, and then put back on gold. You should have 4 choppers, and 8 peons on gold. Pump level 3 ogres constantly and pull a chopper from wood whenever you need a farm. I rarely use this order, but it's fun to play around with once in awhile because you get ogres fast, and you can keep pumping them. Other than that, it doesn't give you many options :).
Things to watch for
You do not have much room to build. You have to plan your wallin very carefully. You have to be able to fit 2-3 barracks, a smith, mound, and mill somewhere. And you won't
have much wood chopped out for you by the time you need all of this stuff. There are a few things you can do to help.
Sometimes you will lose many ogres, and other games you won't lose many at all. You have to plan your farm building carefully, depending on what the enemy is doing. You don't want to build your food up to 33, and only have 5 ogres (21/33 food).
A real game...
This screenshot is a game where I used this strategy. My ogres in the screenshot, are in my dead allies start base. You can see that I'm razing whites base, who did a heavy rush, and then tried pumping knights. The orange guy (the guy who is requesting a screenshot here), killed my catapult by slowly working away at it with ogres. I could not get any closer to his line, so I couldn't do any damage to his peons. However, he tried to get fort, and because I had done this low peon order, I had way too many ogres for both of them.
Also check out this related thread regarding getting fast ogres with a 2 Hall, posted by Ash.