Mordor:
Once the bastion of Sauron, Mordor is now a dead land. Very little of anything is alive on the Plain of Gorgoroth. All of Mordor's forts and bastions of power were destroyed with the end of Sauron's power. Careful to expose, destroy, and cleanse all of Baradur's vaults, the final, mighty fortress of Sauron is truly dead and none of the horrors Sauron made there have lived to trouble the 4th Age.
Other areas of Mordor, however, are not as carefully cleansed. The valley of Minas Morgul, though cleansed and left alone for seven years by decree from King Elessar, has attracted darkness from monsters fleeing Moria and the ruins of Dol Guldur in Mirkwood. Though watchful eyes are watching the valley from Minas Tirith, there are places in the ruins of the Morgul Vale that are not seen, caves and vaults not found in the aftermath of the War of the Rings. In these vaults of the Witch King, Lord of the Nazgul, abominations still exist and are beginning to seep out into the world, and to plan their own designs. Also, the inhospitable, impassable mountain walls of Mordor have become the refuge of foul, polluted beings. Shelob, though dead, still left many powerful, minor kin alive in those mountains. With the end of the war, these mountains have become the hunting grounds of these spider-children of Shelob, feeding off of who-knows-what. Rumors and seemingly far-fetched tales by explorers are now beginning to reach the ears of officials in Minas Tirith and Osgiliath of the horrors around the Morgul Vale and adventuring parties are sent to explore new rumors as they surface. Owing to the fact that a number of those parties do not return or else return with horrifying tales, it confirms concerns of the officials that something evil might well be blighting the cursed valley again.
Mirkwood and the Wilderlands (Rhovanion):
Though Mirkwood was cleansed at the end of the War of the Rings, with the passing of many of the strongest elves from Middle Earth, including Legolas' kin, the elves of Mirkwood saw a great decline in their power. With this decline, their vigilance in the south of Mirkwood was not complete. Believing that Dol Guldur, the sanctuary of Sauron after the end of the Second Age before he returned to Mordor, was fully cleansed and destroyed at the end of the Third Age, the elves did not notice the slow trickle of evil from the ruins. Not all of Sauron's labs and vaults were uncovered, and his deepest vaults eventually opened up in the Fourth Age, opened by foul creatures. Also, evil took refuge in the darkness of southern Mirkwood. As the Fourth Age deepens, the entire south of Mirkwood is a dangerous affair for anyone traveling through it. There are no roads or safe passages through it, and is generally avoided at all costs. The elves of north Mirkwood do not have the strength to search out the evil and destroy it by themselves. Instead, there is a constant, low-level war waged under the boughs of the woods, fought mainly by elf Rangers and Druids against the evil centered around Dol Guldur. The actions of the elves is to contain it, rather than to eradicate it since they don't have the strength of their ancestors. Their efforts are largely unseen and unheard in the settled lands of Arnor/Gondor and Rohan. Additionally, the unholy Church of Melkor has recently seized control of Dol Guldur and enlisted many of the foul creatures under its control as guards and agents. In addition to the Morgul Vale, south Mirkwood has once again become a bastion of evil. There are even reports of multitudes of undead now roaming the cursed forests of southern Mirkwood.
With evil spreading out from southern Mirkwood, the Wilderlands have become the most dangerous they've been in over three generations. Many monsters now lair in the vast regions of Wilderlands, hidden in the wilds from the dedicated hunters of the King. This area of Middle Earth is a common location for adventurers to search out glory, treasure and danger, and remains an unsettled, dangerous region to cross.
Harad:
The regions of Near Harad and Far Harad are both exotic and barren. The lands give rise to exotic peoples and culture and many strange creatures, the best known of which is the "oliphaunt" or Mumakil. Populated by the Haradrim, a nomadic desert-living race, the sands and forests of Harad have only been explored from outside by the ancient Numenorians and the Nazgul. These people, therefore, are barely understood by those in the northlands.
After the fall of Sauron at the end of the Third Age, King Elessar granted amnesty to the Haradrim in return for peace and fealty from them. Determined never to fall under the clutches of someone else again, and humbled by the mercy of the new King, the Haradrim have walked the path of peace ever since. As a people, they adhered to conditions placed upon the Mercy of the King so well that Elessar's grandson released the Haradrim from the service of Arnor/Gondor and granted political autonomy to the nomadic tribes.
As the psionic talents of certain family and tribal bloodlines have risen to the notice of the unified kingdom, the Haradrim have been careful not to use this power to provoke the King. Instead, it is used to protect their trading caravans and defend against the predations of the Yuan-ti, currently infesting the southmost tropical forests and southern deserts of Far Harad. Despite the threat, the Haradrim maintain their ancient ways, as steeped in culture and rich in history as any kingdom of the north. Along with their Mumakil, the psions and soulknives of the Haradrim strengthen the battle capabilities of the Haradrim warriors against their reptilian enemies.
Any and all psionic characters have blood tracing back to a full-blooded Haradrim family member, either the father or mother, or both in most cases, making this the region most likely for psionic characters to originate from.
Although the Unholy Church of Melkor has attempted to sway the Haradrim into its service, that effort has failed entirely. And since the dry conditions of the southlands don't lend too much in the way of large amounts of buried dead, there isn't much for the clerics to use to raise undead in the region. As such, undead are not much of a concern to the Haradrim as compared to other regions.
"Are you sure you want to do that?" - Most important question I can ask you as a DM. So pay attention!
http://www.opengamingfoundation.org/srd.html (3.0 SRD)
http://www.d20srd.org/ (3.5 SRD)