dalaran
I keep some of my f2p horde hearths in Brill. Profession trainers, some class trainers, a quick (and not that it matters, but free) flight path to right next to the Undercity bank if you don't feel like walking, zeppelins to STV/Org and the Silvermoon Portal.
the FP that is near gurubashi arena. from there, i can go to gromgol for zepplin to UC or ORG. but most importantly, when i am late, i can get to the arena fast