This is pretty awesome, and has had me in tears of laughter for a few hours now.
You only need 5 minutes and a few hundred gold.
Step one - Go run Scarlet Halls (Doesn't need to be heroic mode) At the last boss, turn right, and you'll see a blue book on a book shelf.
It'll give you this.
Ancient Tome of Teleport: Dalaran - Item - World of Warcraft
Which will teach you this.
Ancient Teleport: Dalaran - Spell - World of Warcraft
Cool, I can anciently teleport to Dalaran? Wrong! It teleports you to the Dalaran crater. About 200ft up in the air. (See what I'm getting at, here?)
Now, Teleport to the REAL Dalaran. And go find this NPC.
Endora Moorehead - NPC - World of Warcraft
She'll sell you the portal version of this spell.
Ancient Tome of Portal: Dalaran - Item - World of Warcraft
Which teaches
Ancient Portal: Dalaran - Spell - World of Warcraft
Now, go back to your capital city and give free ports to Dalaran! The portal looks identical, and just says Dalaran.
Except they'll teleport in mid air and fall to their inevitable deaths. As long as they're not on a flyer. Tell them to dismount, or put the portal inside the SW Keep/Garrosh's Room.
Have fun!
-Hellson.