If you're planning on entering Northrend at 68, or if you're going to bring a toon that's new to 70 and isn't sporting a lot of good gear yet, setting aside a few choice consumables may help ease the pain while you're leveling. Even if your character's well-geared, you can take advantage of the early-bird specials being offered by a number of vendors in Azeroth and Outland who are already selling Northrend-level food and drink like Pungent Seal Whey. Check in with your local innkeepers to see what they have stocked, sell off the Outland-level equivalents, and set aside a few stacks of upgraded food and drink from vendors with whom you probably have a reputation discount. This will save you some time and gold before you board a zeppelin or boat for the north.
If you're still leveling cooking, now's a great time to get to 375. You can also lay in a stash of buff food that will not only help get you the achievement The Outland Gourmet, but will help you complete The Rokk's daily cooking quests a little bit faster (and the Rokk has an achievement of his own). And it certainly won't hurt to have some buff food around for your first few dungeons.