A fair number of folks I know, including me, are or have been or are going to be leveling characters through the 60s as Lich King approaches. Path 3.0.2 reduced the cost of 60s levels by 30%, which allows for some fine-tuning: doing just stuff you find fun will move you along fine.
There's some great fun buried deep in various quest chains that a lot of folks either never did or maybe did with main characters long ago and have forgotten about. Here are some of my favorites; please feel free to use comments to suggest more.
Pilot a Fel Reaver!
Sure, it's only for five minutes, but the fact is that a quest - The Fel and the Furious, in both Horde and Alliance versions - lets you pilot a fel reaver and destroy infernals. You can fire missiles and do a couple of different attacks on the demons trying to stop you. It's glorious.
The quest chain is similar for both factions. You start by fighting infernals right outside your faction's main base (Horde or Alliance as may be). You'll go repeatedly to Legion Hold, and spend a while at the Deathforge, then back to Legion Hold. Finally you have the means to teleport to a remote Burning Legion infernal assembly base, way the heck on the north side of Shadowmoon Valley not otherwise accessible without flying mounts. There it is you meet your big chugging destiny.
Help a Village Full of Ghosts!
Way in the southeast corner of Netherstorm is Kirin'Var Village, founded by an offshoot group of the Kirin Tor. They wanted to do some good arcane work in the magic-rich environment of the Fields of Faralhon, but it got blown up and subjected to sustained mana-ravaging industrial-scale magic, and Netherstorm is what's left. The ghosts there, and the archmage who's the last living member of the expedition, need some help. You can do it. You can also, and I'm not making this up, escort a ghost cow back to the remains of her barn.
The quest chain's available to both Horde and Alliance. It starts with The Archmage's Staff, from high elf apprentice mage Ravandwyr, on the southwest side of Area 52. Once you get to Kirin'Var, there will be a lot of separate side quests; you'll want to have quest slots free for this.