Khajiit Caravans

The Khajiit Caravans are groups of traveling merchants from Elsweyr. The caravan system in Skyrim consists of three roving bands of Khajiit merchants, and their respective entourages. The caravans are not allowed inside the cities of Skyrim, so they must make camp outside the walls. They can be found walking the roads of Skyrim in between camp locations, and will even pause to do business with the Dragonborn while on the move. Upon completion of the Thieves Guild main and restoration quest-lines, an alliance can be made between the two groups unlocking certain Caravan merchants as fences.

Ri'saad's Caravan
The caravan led by Ri'saad is the wealthiest of the three, and enjoys the most lucrative trade route. Ri'saad's route travels back and forth between Markarth and Whiterun. The caravan features a variety of wares and offers a tanning rack, for crafting purposes. Ri'saad is accompanied by Atahbah and Ma'randru-jo. The trio is protected by Khayla, who also offers training in Sneaking up to 50 (Adept). Ri'saad and Atahba both can become fences.

Ahkari's Caravan
The caravan led by Ahkari follows a route that includes Dawnstar, Windhelm, and Riften. The caravan offers a variety of goods and services. Ahkari is accompanied by Zaynabi, and the pair are protected by Dro'marash and Kharjo. Ahkari also offers training in Pickpocket up to level 50 (Adept) and Dro'marash offers training in Speech up to level 50 (Adept). Kharjo is also available as a follower, provided his stolen Moon Amulet is retrieved from the bandits who took it. Zaynabi can become a fence.

Ma'dran's Caravan
The caravan led by Ma'dran has profited greatly from the Stormcloak rebellion, as weapons and armor are the caravan's specialty and their route runs from Windhelm to Solitude. Ma'dran is accompanied by his two guards, Ma'jhad and Ra'zhinda. Ma'jhad also offers training in Lockpicking, up to the Expert level. Ma'jhad can become a fence.

Trivia

 * Ri'saad is marked as essential due to his relevance in the quest, Deliver Moon Sugar to Ri'saad.
 * Khajiit caravans are a good place to buy lockpicks, often having 30 or more in stock.
 * Ahkari's stock can be found behind the trees near the Iron-Breaker mine in Dawnstar in a glitched merchants chest, (the chest is in between some rocks by the tree to the left of the mine when facing the mine entrance).
 * Ma'dran's stock chest can be found in the middle of the first stone wall, (side closest to river), outside Markarth where Ri'saad sets up his shop.
 * Ri'saad's stock chest can be found near where Ma'dran sets up shop outside of Solitude. Found by crouching and searching around the area between the small tree and the rocks off the road approaching Solitude.
 * The above chests mentioned are "invisible" and the only proof of having found them is the "open chest" prompt. No bounty will be added for taking items from them and they will restock after waiting 48 hours and viewing the sales inventory of the merchant the chest belongs to.
 * Khajiit Caravans always have a fresh stock of Skooma and Moon Sugar.

Bugs

 * Sometimes Ri'saad will not show up in Whiterun after completing the quest "A Blade in the Dark" with Delphine. His other three followers will still be traveling but will not setup camp. Ri'saad could be found outside of Windhelm where Ma'dran's Caravan sets up shop. Ri'saad will stand there with Ma'dran as if having conversation; Activate Ri'saad to barter, Ma'dran will not, saying that he has no wares. They seem to be stuck there, unable to move. (Unconfirmed: Xbox360 - needs more testing).
 * The remaining three can be stood next to each other, which makes the "Contract: Kill Ma'randru-jo" quest given by The Dark Brotherhood look hard to complete without a bounty. Although, sometimes they do not seem mind if he is killed next to them and talk to the Dragonborn as they normally would (tested twice, first time worked, but when loaded from a previous save and talked to, was then attacked - links into the below point also).
 * This error might be corrected in the course of completing "Find the Thalmor Assassin." Ri'saad can tell the Dragonborn that J'datharr is not a caravan member, and his participation seems to fix the error. However, this requires Malborn to have survived "Diplomatic Immunity."
 * Sometimes the Khajiit in the caravan appear, but their tents do not and they do nothing but stand still. However this is rare and usually fixes itself, after the first encounter with the bug, but there have been cases where it happens nonstop, but one can still trade with them.
 * Sleeping 5~6 days in one of your home should fix it. (Unconfirmed: Xbox360 and PC. Tested on PS3)
 * The tents for the caravans show up in the appropriate locations, yet the Khajiit are not there. (Has happened outside of Solitude, Windhelm, Riften, Whiterun, Dawnstar, and Markarth.)
 * Solved by waiting for 3 hours.