The Starcraft Command
This is a great strategy all around as long as the person that you drop on does not have a large amount of lurkers/dark templars or air defense. Even with 1 or 2 turrets you should still be able to take out a lot of stuff.
First build 8 SCV's and with the 8th build a supply depot. Then continue to build 2 more and then build a barracks. With the 10th SCV build a refinary. Then build 3 more SCV's. The first 2 go to your refinary, and the 3rd you use to build another supply depot. Then build another SCV (should be 14 now) and with him build a factory. Your barracks should have been completed already and as soon as your factory has begun build a bunker. Pump out 5 marines. (4 to go into the bunker and 1 to scout with.) Once your factory is done build a Starport with that SCV. Then once that is building put a Machine Shop on your Factory. Then build 3 more SCV's. With the first build a barracks. With the second build an academy. And with the 3rd build another barracks.
Once your Starport is done immediately put a control tower on it. Build 18 marines, 6 medics, and 3 dropships. Fill each dropship with 6 marines and 2 medics. Drop them near the minerals or at an open spot. (Please don't be stupid and drop near the front of their base. I've seen it done).
If this fails you should have a lot of money and build some tanks, and do sort of the same thing, but just with tanks in the drop. I doubt it will fail though.