Well I discovered this by freak accident today and might aswell post it here, I don't consider this a huge exploit or anything, but it might be fun to do for some.
Alright, so to be able to fly in dalaran without the debuff you normally get, you just have to enter one of dalarans named spots (aka subzones; Silver Enclave, Violet Citadel ETC) faster than you get the debuff, and you'll be totally safe to fly around in dalaran AS LONG as you DON'T fly into a zone set as "Dalaran (Sanctuary)" because that will give you the debuff. Now, to get into one of these zones you WILL pass through "Dalaran (Sanctuary)" BUT if you do it fast enough, you will enter without debuff.
In my video I go back and forth really quick which I discovered wasn't really necessary, just try to enter the zone "Silver Enclave" fast. I've only tried this outside of the silver enclave and violet citadel, but afaik it should work anywhere where you can reach the zone fast enough, I don't know if you can make it easier by making your wow lag, it might, but note that I have very low latency to my server.
feel free to find some fun uses for this and post em:
[YT]http://www.youtube.com/watch?v=BrkcCn2MmeU[/YT]
(please note that video is 'processing' at youtube when i submit this so it might not be viewable JUST YET)