Undead Fast Expand! (Submitted by Brain_Dead)
For the Undead, this works well in small games, solo or 2v2. Some of the most powerful units in the Undead race are the Abominations and the Frost Wyrms (besides heroes). Their weakness is their attack speed (2 seconds cooldown!), so the easiest way to handle that is to bring Necromancers to cast Unholy Frenzy on as many of them as possible. Although it drains 4 hit points per second, it doesn't really matter against most attacks because they are good meat shields anyway (besides having a Crypt Lord...). Those heavy units just took care of their weakness, so have fun against that combo!

[ Click to Enlarge - 176 KB ] In this funny screenshot, an Undead player is fighting the Creeps while expanding at the same time! You can see the Gnoll behind the Haunted Gold Mine as the Dread Lord is fighting him. The player put down some Blight using a Sacrificial Skull so that he could summon in Spirit Towers very quickly.