There were a few good theories there about just such things. Fortunately, I have the archive copied to my PC and I found a couple that apply. The first one is from Cannoli, and the other from Bobsledai, (who was quite good at coming up with ideas about such anomalies.) Enjoy!

How the Green Man's place works
Submitted by Cannoli
Posted on 6/24/2004 3:48:14 PM

In the Eye of the World, chapter 51, "Against the Shadow," after defeating Aginor, Rand moves mysteriously from the hilltop where he wrested the power of the Eye of the World from the Forsaken, to the pass of Tarwin's Gap where the Shienaran forces fight a Trolloc host. When he moves from the battlefield, it is to a staircase that appears out of nowhere. The following description is given.

"Darkness surrounded him, the utter blackness of total nothing. The steps were still there, hanging in the black, under his feet and ahead."

The description bears a close resemblance to the means of One Power transportation known as Skimming. When it is first used deliberately by Rand in The Shadow Rising, he finds himself on a staircase, until he realizes he can make the platform carry him, by spotting Asmodean doing the same thing. Subsequent uses of Skimming show the surface to be mutable by the will of the channeler who opened the door to Skim. As Rand is used to thinking of transportation as leg-powered or involving wheels, the idea of a moving platform did not occur to him until he saw it was possible.

According to Asmodean, in The Fires of Heaven, the place a Skimming platform moves through is "a dream of a dream." A place described in terms of dreams, that is mutable by a person's will, strongly suggests Tel'Aran'Rhiod in the Wheel of Time. Verin describes Tel'Aran'Rhiod as a place surrounding the other worlds of the Pattern, existing outside of these worlds, but touching them. Ba'alzamon enters the dreams of the three ta'veren and exerts his will on the surrounding environment. As Egwene, a Dreamwalker with some training in controlling dreams, cannot even control her actions when she enters the dream of an untrained man who is totally unaware that she is in his dream, this suggests that Ba'alzamon pulled them into Tel'Aran'Rhiod, which the Wise Ones claim is something evil and done by the Shadow. When Egwene contemplates this action in A Crown of Swords, she describes it as pulling the dreamer into a "part" of Tel'Aran'Rhiod, over which she has control. Taken together, these facts suggest there are more than one of these "dream worlds" in which reality can be controlled by the right person.

I believe the Green Man's place is something similar. Getting there in the first place is difficult enough. As Moiraine says in The Eye of the World, "No one finds the Eye of the World…unless the Green Man wants them to find it. Need is the key, and intention." Loial later says, "No two…have found it in exactly the same place. The Green Man seems to be found where he is needed." When they arrive unexpectedly in the Green Man's place, the Green Man himself states, "This place…is always where it is. All that changes is where those who need it are." That is crucial to remember - it is the people who travel to the Green Man's place, it does not move, whatever their perception is.

Many people have speculated that Jordan changed the rules for Traveling halfway through the series, as the early books implied it was teleportation, and Rand actually appears to teleport from the hilltop in the Green Man's place to Tarwin's Gap. There is no description of any sort of effect like a gateway or other manifestation of some weave of the Power, even performed unconsciously. He is simply in one place and then another. The closest matching method of moving from place to place is how person in Tel'Aran'Rhiod can move themselves without crossing the intervening distance.

Dreamers who enter Tel'Aran'Rhiod can also travel to a place with no specific destination in mind, by concentrating on a particular need. Even if the person has no idea what that need is, they will find themselves in the general area, and getting closer each time they attempt it. Characters in the story have used this method to find things as specific as a particular unknown object that is a threat to someone, or as general as something to motivate the Salidar Aes Sedai to support Rand, or as vague as "…where I need to be…" Another interesting fact of need-based transportation in T'A'R, is that no one can seek the same thing twice, which is also the case with the Green Man's domain. Moiraine, and possibly Lan went there a second time, but they were in the company of three ta'veren for the second trip, one of whom was about to fulfill the purpose for which the Eye of the World was created.

The Green Man's place is not in Tel'Aran'Rhiod, and I believe it does exist in the physical world the same as Tar Valon or the Two Rivers, but the means of getting there is related to the same principles that govern the places between the Pattern such as Tel'Aran'Rhiod (where the Heroes of the Horn wait until their souls are reborn to meet the Pattern's NEED) or the Skimming place(s). Thus, when Rand needed to be somewhere else, he found himself in Tarwin's Gap. He is still not conscious of how he channels the Power, so the fact that he never tried to go anywhere is not necessarily conclusive - he simply isn't yet aware of the mental process to decide he needed to be elsewhere - much the way people channel unconsciously but aren't aware of making the weave until they see the result, and cannot remember what they did later.

The exact mechanism may be some form of ward placed by the Aes Sedai of the Age of Legends in an effort to keep it from being despoiled by those who would interfere with the purpose of the Eye and the artifacts stored within. The banner found in the Eye was in the possession of the same group that also had Callandor, so they would have been quite capable of setting up a ward or weaving that would last 3,000 years. Since Tel'Aran'Rhiod was apparently accessible to all the Forsaken (nearly every living Forsaken has been seen in it since the readers learned of its existence), this suggests it may be reached by a weave of the Power, and not just in the flesh, and of course, the Skimming place is also accessible by the One Power. It would also explain the ability of the Forsaken to find and enter the Green Man's place when Myrdraal and Dreadlords were apparently unable in the 3000 years since its creation - the Forsaken have access to Tel'Aran'Rhiod, and/or would understand the nature of the ward.

The Green Man's Place
Submitted by bobsledai
Posted on 11/25/2002 1:51:58 PM
I've been thinking that maybe the Green Man's place where the Eye of the World was found was somehow an intersection of the real world and TAR.

The quotes:

“Are you going to leave Egwene to face it alone?...Light help me!” (EOTW, ch. 49, p. 739, paperback).

“‘When this place was made, it was made so that none could find it twice. How have you come here?’

“‘Need,’ Moiraine replied. ‘My need, the world's need.’” (EOTW, ch. 49, p. 741, paperback).

In the first quote, Rand, while running from the Worms, becomes concerned for Egwene. Since we know he channeled in order to save Egwene (with Bela), then likely his concern for her in this situation became one of need.

The second quote tells us that need is the requirement for finding the Green Man's place, or having it find you. Moiraine says it is her need, but with the first quote I believe it is actually Rand's need that brings them there.

Nynaeve learned from the Wise Ones that focusing on need in TAR will take you to whatever it is you need: “According to you, the Wise Ones said the stronger the need the better...” (LOC, ch. 13, p. 331, paperback).

I believe that the Aes Sedai who made the Green Man's place knew that people traveling in the Blight are bound to have great need at some point or another. So they put it there, using the Power to form an intersection between the real world and TAR. This would allow them to place real items there, as well as the Eye, but protect it from being found by the wrong people. Certainly no one following the shadow would see it as NEED. (Unfortunately, Mat and the dagger led two Forsaken there).

As to the reason why it could only be found once by a person, look back to Elayne and Nynaeve's search for the Bowl of Winds. While in Ebou Dar, they disagree as to how many floors the building which holds the Bowl has, which is resolved in COS, ch. 38, "Six Stories." If they disagreed, why not simply go back to TAR and search again? I doubt RJ made them that woolheaded, so I believe that for them as well they cannot find the same thing twice using need in TAR.
Burr says: This could possibly also explain the instant traveling that Rand does to reach Ishy. He wouldn't need to weave a Gateway to travel quickly if he is in T'A'R. However, I wonder if it would be because there's something special about Someshta's garden, or if it would have more to do with getting deeper into the Blight and closer to the Bore. The Aes Sedai who created the Eye of the World may have hitched a ride on pre-existing dimensional funkiness.