For those druids amongst you, Dylan and Cody have put their heads together and provided a complete list of all the trees you can tree walk to. Below is the list ordered by tree name, with links to the maps if they've been mapped here yet.
Agnes - Near the entrance to Heiraktazin.
Alfom - At the base of a huge tree (Bh) in Darkenwood.
Archpine - A campsite in the Arch Woods (Ca) in Lake Yeven.
Austin - The Spine of Mon Crewyll.
Belmirek - Northern Lordaeron between the elven ambushers and the troll campsite.
Bluebell- West side of Unicorn Run, at the Peaceful Glen (Pg)
Braeburn- Edge of the Campsite (Ec), just inside the Battle of Bones
Breadfruit - Inside the Clock Tower
Canis - Just north of Ungrim's Tavern (Un) in Ravenclaw Woods & Wilds.
Cassandran Keep - Fortress Courtyard (Fc) in the Cassandran Stronghold.
Colleen - In the Centre of Clearing (Cc) in Spiderhaunt Forest, same room as Silver, Druid guildmaster.
Conferva - Under the ship to the south of Aquallia.
Cyra - Darker Forest Path (Df) near the entrance of Crysal Lake.
Drachir - West of the far hills, southeast of the Fields of the Dead in the Reaching Woods, near Isela.
Drury - Southwest of the township in Elf Shadow.
Edgar - Hidden Tree Sanctuary (Hi) near the Ebony camp in the Ivory Kingdom.
Everil - Myth Drannor.
Evermore - Just inside the entrance to Castle Dreadyre, near the Lost City.
Flavia - South west corner of Golothaer just south of Frizzel.
Felicia - Neverwinter Woods.
George - Near the enctrance to Dhedluk in Sea of Fallen Stars and Westgate.
Graymoss - Path in the Swamp (Ps) due south of Blackwater Swamp in the Troll Moors.
Grimbranch - two east of the cart at the entrance of Jayven.
Grippa - South end of Jayven near Scree.
Gypsie - Peaceful Clearing (Pc) in the City of Khmer.
Gzoobaa - A Huge Aspen Tree on the east side of the city in Sulphur Winter.
Hosea - Infested Tree.
Kalos - Just north of the Cobblestones (Co) in Red Fog Graveyard.
Lewis - Near the centre of the town of Mistledale to the south.
Lisa - In the Kings Orchard in the Dark Castle of Khmer.
Magnus - The Common (Tc) in Shadowdale itself.
Melancholy - The Mists of Nartok, you'll need sneak or the wolf-men will gobble you up!
Mickey - Unknown as yet!
Nautilus - The Murky Deep.
Noble - In the garden to the south west of Rhyiana.
Patches - Ovideo's Crossing. Very dangerous, as level 50 wererats running around.
Peter - Outside the Dome (Od) in the Lost City, 3s7w to the Well (We).
Phlan - Civilized Phlan.
Promise - Meadow Creek.
Ruha - Just south of the purple worm in the middle of Anauroch, the Great Desert.
Serenity - South of Allaturtle, in a forested area south west of Meadow Creek.
Simona - On The Beach (Be), to the south of Vodalia.
Spiny - North of the southern entrance to Lordaeron in the Dragonspine Mountains.
Thorus - Just north and west of Krok in Birch Island
Tres - Near to Shadowdale in Daggerdale, 2e2s2e4n to The Common.
Wist - On the trail to the underground part of Rocky Point, south is the Inn.
Wyrmwood - Forest of Tethir.
Wynter - Northwest corner in of Frost Mountainin the Frost Forest (Ff).
Xavier - Centre of the forest to the north east of Lopan. Peltor the ranger is here.
Zadoc - Unknown as yet!
Zzutam - A gravel road, north west side of the centre of town in the Vale of Frost