I started with two accounts, each half full of 70's mid way through Burning Crusade.
Added three accounts.
B > C
A > D > E
Boosted B/C and D/E, with A.
I did... Druids, Hunters, Priests and Shammies, during my RAF.

I have since started Warlocks.
And am thinking of Pallies, Mages or Rogues.

Wish I had, done some of those four with the RAF.
I had more then a month of RAF remaining, when I quit leveling new teams and started on the Shammies.

The un-used toons aren't a waste.
I've got 29 alchemy transmutes a day, which has translated into just over 500k in almost half a year of transmuting (more then half a year, but did almost nothing over the summer).
The Priests are fun, and tempting to take beyond 75th (minimum level, for a 525 Cataclysm tradeskill cap); the Hunters (and DK's and Mixed Team) won't likely be played a whole lot in Cataclysm, but that is still 15 extra transmutes a day.