Much of my effort so far in Northrend has been to get my mage, Atoz, to Dalaran as quickly as possible. This is integral to transportation around Northrend.
Dalaran. The city of mages floating above the Crystalsong Forest in Northrend. Only mages can get there of their own accord before level 74 (without a friendly mage portal - that's why I'm putting forth all of this effort with Atoz, it will be a nice perk for my friends and rather profitable to sell ports). The mages get a quest at level 71 in Star's Rest in Dragonblight that rewards with the Teleport: Dalaran spell. Then presumably they port to Dalaran and learn the portal spell to bring others in.
So, I found the flight paths for both Howling Fjord and Borean Tundra. I eventually got to the Tuskarr boat docks and boarded the turtle boat to Dragonblight and connected between the two areas (picking up flight paths along the way). Later I made it to Star's Rest, got the flight path and now I can get back there easily for the Dalaran quest. Now all I have to do is to 71, head back to SR, do the quest and arrive in Dalaran! Whew.