Here's the copy/paste version, hopefully that's ok since I gave attribution:
Herbalism 1 to 300 Guide
1 - 50
Collecting Silverleaf and Peacebloom
Â· Mulgore. Just do circuits round the base of Thunderbluff picking Silverleaf and Peacebloom.
Â· Do circuits around Dolanaar heading South East around the lake and back upto to Dolanaar, if your Alliance or complete circuits of Elwynn Forest.
Â· For Undead, try starting at Solliden Farmstead in Tirisfal Glades, run north to the mills, loop round and back south past Stillwater Pond and onto Cold Hearth Manor and Nightmare Vale. Then back up to Solliden Farmstead again. (Thanks to Olmolmtyr for info)
You can find Peacebloom and Silverleaf in abundance around your main starting area (not in it, around it). So the first 50 levels should be really easy.
51 - 70
Collecting Mageroyal and Earthroot
Â· Go west from Crossroads then head north before the entrance to Stonetalon Mountains and follow around to where the harpies are, then head east back to the Gold road and then south to Crossroads again, picking Mage Royal, Earthroot, Peacebloom and Silverleaf as you go.
Â· For Alliance start in the north of Westfall and follow the coast south to Deadmines and then head straight to Sentinel Hill and back up to the north again, picking Mageroyal.
Â· You can also run circuits of Gol'Bolar Quarry in Dun Morogh, collecting Earthroot as you go. (Thanks to Flareon for that info)
71 - 100
Â· Same route as above (for Horde), but extend it east to Sludge Fen, picking Briarthorn now.
You could actually extend your runs to encompass the whole of The Barrens, as this area is absolutely chock full of Briarthorn and other herbs. It's possibly the best area to get your herbalism trained up.
Â· Southern part of Silverpine Forest, from Pyrewood Village to the Entrance to Hillsbrad Foothills and back again.
Â· Same route as above (for Alliance) or do circuits of Twilight Grove in Duskwood.
Â· Also for Alliance, just wander north to south in Darkshore for loads of Briarthorn.
Â· The eastern side of Loch Modan is also a great place for Briarthorn.
Â· You could also do circuits of Lakeshire in Redridge Mountains.
101 - 115
Â· Start at the Ramparts in Ashenvale and head north-east to Splintertree Post (dont follow road, try to go as straight as you can, you'll find more herbs that way), then head west from Splintertree Post towards the first bridge. Head south from here past the Moonwell and then back west to the ramparts when you reach the edge of the map. Pick Bruiseweed as you go.
Â· Stonetalon Mountains. Go to Camp Aparaje, head west to the Grimtotem Post, then south to Malaka'jin, then east to the Greatwood Vale. Nice run of Bruiseweed there.
Â· The Field of Giants in Southern Barrens or between the two Razorfens.
Â· You can also circle to the north of Mystral Lake for Bruiseweed or to the West of Astranaar in Ashenvale.
Â· Windshear Crag in Stonetalon Mountains.
Â· The eastern coast of Loch Modan.
Â· Circuits of Stonewatch keep in Redridge Mountains.
116 - 125
Collecting Wild Steelbloom
Â· Go to Stonetalon Peak and do circuits of the small area around the Alliance Town and the Talon Den collecting Wild Steelbloom.
Â· For higher levels do full circuits of Arathi Highlands, sticking to the mountain sides (as this is where you'll find Wild Steelbloom)
Â· Nek'mani Wellspring in Stranglethorn Vale.
Â· The Zuuldaia Ruins, north of Grom'gol in Stranglethorn Vale.
Â· Go from Black Channel Marsh in the Wetlands to the Angerfang Encampment, taking in Whelgar's Excavation Site as you go.
Â· Go from The Field of Giants in southern Barrens to the two Razorfens and back up again.
Â· Between The Great Lift and Highperch in Thousand Needles.
*from now on your going to be doing circuits of the full map, so you'll have to learn your own paths.
126 - 160
Â· Full circuits of Ashenvale to collect Kingsblood.
Â· Circuits of The Charred Vale in Stonetalon Mountains.
Â· Full circuits of The Wetlands.
Â· Full circuits of Hillsbrad Foothills.
Â· The Misty Reed Stand in Swamp of Sorrows.
161 - 185
Â· Full circuits of Swamp of Sorrows to collect Fadeleaf (sell these to Rogues for a good profit).
186 - 205
Collecting Khadgar's Whisker
Â· Full circuits of The Hinterlands to collect Khadgar's Whisker.
Â· The Witherbark Village and Ogre Compound in Arthai Highlands.
Â· You can also stay in Swamp of Sorrows, as there is a decent amount of Khadgar's Whiskers there.
206 - 230
Â· Full circuits of Searing Gorge to collect Firebloom.
Â· Full circuits of Blasted Lands.
Â· Tanaris also has a lot, but doing full circuits takes time. You can divide Tanaris into four and do circuits that way.
231 - 250
Â· Full circuits of Felwood to collect Sungrass. This is actually more of a zig-zag pattern, rather than a circuit (also try to do the Cleansing Felwood quest and pick up Windblossom Berries, Nightdragons, Whipper Roots and the odd Songflower Serenade buff when needed).
Â· Feralas is also a great place to get Sungrass. You can make two circuits here. One that starts in the very north west at The Ruins of Ravenwind and runs south to The High Wilderness and one around The Lower Wilds, Lariss Pavillion, Grimtotem Compound and Woodpaw Hills, all near Camp Mojache.
Â· You can do circuits around The Forlorn Ridge in Azshara.
Â· You can try the main path through The Hinterlands too. As you follow it one way, stay about 50 metres from the path and then do the same the other way.
251 - 270
Â· Full circuits of Felwood to collect Gromsblood. See above notes.
Â· Do circuits of Mannoroc Coven in Desolace for Gromsblood too.
Â· Full circuits of Blasted Lands.
Â· Demon Fall Canyon in Ashenvale, not many people bother with this area, so although its small, it can be good for farming Gromsblood.
271 - 285 or 290 (see below)
Â· Full circuits of Un'goro Crater to collect Dreamfoil.
Â· Two good routes in Azshara are:
Â· From The Forlorn Ridge, head south east to the Ravencrest Monument and back again.
Â· From the north of the Ruins of Eldareth, head north east to the Jagged Reaches and back again.
285 or 290 - 300
From 285 you can get Plagueblooms from doing circuits of Eastern and Western Plaguelands and Felwood, but if your not competing against a load of other players, try to collect Icecaps from Winterspring, as they will sell for more money
Herbalism 300 to 375
Just threw this together really quickly, if it's of use to anyone I'm glad, if it's not then just ignore it.
300-330 (or 345 if you so choose) - Felwood
I know you were all probably hoping for something alot more exotic and in the outlands, but Felwood really is the place to go if your looking at it purely from a lvling perspective. Due to the hit of TBC there's virtually nobody farming herbs here and you get the bonus of Whipper Roots etc. which while out dated, still aren't on the same timer as pots, so if your a raider they can save your ass.
I generally start at the alliance flight path, going up round the Furbolg village before following the perimeter south. I've included a map for anyone unsure of a route to go.
Pick absolutely everything that is even green to you. Plaguebloom, Dreamfoil and Mountain Silversage give about a level each bush until 330, and whilst the plague that is Sungrass, Arthas' Tears and Purple Lotus are green, they still give a level fairly consistently so it's definetly worth picking them. If memory serves somewhere around 340 Plaguebloom goes green, and you start to get levels less consistently, however you may choose to stay on, especially if you don't have an epic flying mount, for the densely packed herbs, and low demand by pickers, all the time remembering that Golden Sansam, Mountain Silversage and Dreamfoil still sell very well on most servers.
330 (or 345) - 350+ - Zangarmarsh
Zangarmarsh is simply packed with herbs, all of which are useful. My favourite are is the North-West corner, being packed with herbs and Bog Lords / Giants which can be herbalised (If that's even a word) once looted. I tend to zig-zag across it, before moving to the start to do the same, however on more populated servers you may have someone else doing the same, so extending your route to sweep up from the south-west and across the northern border can yield great rewards too. Expect lots of Felweed and Ragveil, with the odd Dreamfoil and Dreaming Glory.
I've included a map despite this route being fairly self-explanitory as with the last one.
Once you hit 350 the world is your oyster really. I chose to continue my Zangar route all the way up to level 375, but it is equally viable to move on to Shadowmoon or elsewhere.