Here I'll throw in some other level stuff too:
The Wind Hag adept is an awesome one to kill since the 4 adds each give adept experience. Between the hag and the adds you can get pretty much all of level 25 in ~5 minutes. Just be sure the people you go with can actually kill her.
The turnin quests in the badlands are good to do if you're 2boxing or can't find a full group anywhere. These quests span the 20s and 30s.
Spectres in GSM or the smaller camps in the badlands are great money and decent exp in the 40s. There aren't really enough for more than a good soloer or 2boxer though, so a full group will be bored.
Other than these, the typical places like Warpstone for the 20s, Kaladim/Kingspass for 30s, Robots for 40s, Lasanth to 55, etc are generally the best places (that's why everyone recommends them, seriously).
Just remember it's almost always better to be in a full group, regardless of zone. 6 people are capable of killing a lot faster than 2-3 and you get the same exp per kill.
18 hours?! Has it gotten easier to lvl since i quit in 04? I remember it taking a good day in a decent group to lvl...
If you're referring to Konad's post, let me clarify. EC/FR/HHK are 65+ exp zones. He either was leaching from uber characters slaughtering the entire zone for cash, or was in exp groups on his 65 monk and also had his rogue in the group. A typical 50s/60s pickup group would not be able to gain experience at a tenth of that rate, if they could kill anything in those zones at all.
In HHK I got a pally friend of mine 60% of level 64 and 12 AAs in about 2 hours, and my monk got 16 AAs that same night (I was still under 50 total, so that rate definitely doesn't stay the same for long.)
Getting a level or two a day at levels 50+ is a more typical rate.