Well, if you've got the skill for it, I would recommend either Ashenvale or Thousand Needles. Mobs range from the 20-30 range, so it might be tough in some places, and others not.
There are alot of other kinds of ores out there too, so good luck finding irons!
Edit: Maps for both...
http://wow.allakhazam.com/db/mapset.html?zone=1001&type=Mining&size=Large
http://wow.allakhazam.com/db/mapset.html?zone=1021&type=Mining&size=Large
And also found out there are some in Stonetalon Mountains
http://wow.allakhazam.com/db/mapset.html?zone=1016&type=Mining&size=Large
Edited, Mar 19th 2007 9:43pm by baveux