Just a few references for those who are trying for certain achievements, because we obviously all like having big numbers to show off.

Outmatched 1v4 Very Hard AI
http://www.youtube.com/watch?v=2P9_O5o4fFg
This works for the 1v3 Very Hard AI as well, since it's just one less to deal with. Keep in mind that it's possible for the 3 AI to be on the same side of the map as you when you do it the map.

Outmatched 1v2 Insane AI
http://www.youtube.com/watch?v=qsKkknfcDWA

Insane AI Blitz
http://www.youtube.com/watch?v=SRb3MU1hI-A
This one actually works every time. I managed it 10 times in a row in 4 minutes each while other methods failed me. It got boring eventually; I dunno how people can possibly have the patience to win 100 times against bots for the achievements.

7 Insane AI FFA
http://www.youtube.com/watch?v=uArcNBo0EWE
Don't use this map. Use Lava Flow because the islands have a double expo and are safer.
Basic idea is:
- Play Terran vs 7 Protoss Insane AIs
- Load CC, fly to island with your SCVs and build base there.
- Tech Battlecruisers asap with 3 starports. Get 3/3 upgrades (Build 2 armories).
- Get Vikings. 2 Vikings/Battlecruiser is recommended.
- Since you'll have a ton of minerals later, make a line of missile turrets around to prevent the last computer from doing mass drops.
- Attack move to base when you have 180-200 food of BCs/Vikings. Make sure you use Yamato Cannons to prevent High Templars from making use of Feedback.

Playing the matches with highest level of AI will also net you the ones for the AI level below it. Insane AI will cover the achievements for Very Hard, Hard, and Medium.