This exploit will allow you to fly anywhere in the old world. Only tested on Scape servers. And only for the Druids.
1) Start in flight form. Use one of the Dalaran or Shattrath portals to one of the old cities (Stormwind, Orgrimmar, etc.)
2) You should still be in bird form but unable to fly. Log out, log in, and you should still have the flight from buff and should be able to fly anywhere. Also works for instances and raids.
*You will fall to the ground when you go into a different zone. You'll still have the buff, so simply relog and you'll be flying again.
Some stuff I've used this for on Scape servers:
*fast travel in old world (duh)
*skip to specific bosses / trash mobs in raids
So far me and a guildmate have managed to get to heroic bosses without touching a single mob and were even able to loot the 4 horseman chest in Naxx. So be creative I guess, sorry if this is a repost.