5-10: worms in konstat in the lower left corner
10-14: rampage through the sheep in kon, with dark crystals and tea leaves making sheep leather as I go.
14-17: warrior skeletons in gusgen mines, they dont link (but will blood aggro) and like everything else that level hit like little girls
17-20/21: if no partys kill goblins in valkrum in the level 10-12 exp camp area, do not go after WHM goblins they are whores
The golden levels:
19-24: Worms in Korrokala tunnel, specifically the I-H 8 camp on map #3, the north side. I've gotten chain 14 'solo' PLing myself before, and I've also (on DRG) gone from 22-24 on the same chain douing with a friend. At 23 some of the worms start poping DC, but at that level its still decent xp for very, very little effort.
25-27 worms in quifum. Possible to go to 27.
27-29: suck balls, sometimes. Giants in quifum. Not the quickest, but suplement with worms bats and skeletons and you have a giant playground of decent xp.
30-34: You can go here earlier if you feel brave, Yutun. Mandys in the first jungle. H-7 is usually free of partys, and as you level up you can take on the goblins roaming around.
Anything i've tried to PL around 30 starts to be horrible, and just a place holder while I LFG as half the time a party is faster, if I can't make one at that level.
http://monsters.ffxi-atlas.com/ is usually where I go to look crap up while I LFG, and thanks to it I PL'ed MNK from 52-72 back when urgan came out. Find a BLM solo guide (I dont have one or i'd give) as usually they target monsters that are good xp vs the squishy, low HP requirement.
I'm definitely checking out some of the other ones mentioned, I just use the above because all the zones are close togther in levels that use the same equipment or allow quick routes back if something more interesting comes along.