Today one of my friends said to me, all of his friends come to play the Wrath of the Lich King, but because of the busy work, he had no level 70 account to play, how sad he is! But don't be so worried, I am sure he will have ideas to get his account to level 70, now let’s come to see the last 5 levels from 75 to 80!

According to Matticus, we can easily know the final 5 levels from 75 to 80.

Zul'Drak – Priests will have a field day in this zone. On one side, you're going up against Scourge forces trying to take over the Troll capital. On the other side, there's renegade Trolls running loose. Your Shackle Undead is going to come in great use here if find yourself getting overrun and overwhelmed.
Sholazar Basin – It seems as though no matter what you do, you just can't get rid of Nessingwary. Get ready for more exotic animals to kill. Note that flightmaster does not become available until after you do a few of the early quests. A plane can't fly until you get the parts for it to become operational again.

At level 77, you'll get access to Cold Weather Flying. In order to continue leveling, you're going to need it for certain areas in Storm Peaks and Icecrown. You won't have to complete an extensive chain in order to learn it anymore. There's a Cold Weather Flying trainer in Krasus' Landing in Dalaran who will gladly teach you this ability for a mere 1000g (depending on your reputation).

Skills
At 75, we get access to a new Shadow spell called Mind Sear. Check out Alex's post for more information on this new baseline ability. At level 80, we also get Divine Hymn. Haven't tried it out yet extensively. It looks like a lot of fun to use in PvP.

Professions
Start working on your professions now that you're 80. You may have to resort to farming them on your own (dual spec can't come soon enough). The auction house has some ridiculous prices up there right now.

Gloves of the Time Guardian
These gloves would be something for early Priests to look at. All you need to do is run Caverns of Time: Stratholme and complete the quest Chromie gives you (A Royal Escort). If you're lucky, a Soul Preserver might drop which will help ease any mana woes you may have.

Moonshroud Robe
Tailors can create this epic level robe (which are extremely expensive). Run Utgarde Pinnacle and accept the quest (Junk in my Trunk) to get a Bauble-Woven Gown instead if you can't afford it.