My personal favorite thing that I came across was the fountain, as is displayed in the video and previously here on WoW Insider. Various lore characters that have been in Dalaran at one point or another have tossed coins in the wishing well, and they come with quotes from the characters. Characters from the games, the novels, everything, they're there. It's really pretty cool.
The more random things are fun, too. The Hungry Tuskarr buff makes me giggle, and the Wild Magic adds a little "Hrmm, what will happen this time?" to the experience. If you're a Fishing fiend, I definitely recommend hopping over to El's Anglin' and taking a look around. The site has pretty much everything you could possibly want as an angler in WoW.
[ Thanks, Shao! ]