Each of the Skirmish Camps has a set of NPC vendors with the following titles:

Skirmish Captain

The "bard" for skirmish traits, the Skirmish Captain allows you to slot and un-slot roles and skills as you like. Additionally, he has the initial skirmish tutorial quest which unlocks Skirmishes and he sells special skills such as the Ultimate skills.

Skirmish Trainer

The Skirmish Trainer allows you to buy and level up skirmish roles and skills. If you don't see something that you wanted to level up, either buy it from the Skirmish Captain or uncheck the "Only Display Earned Traits" checkbox at the top of the Skirmish Trainer's dialogue.

Light Armour, Medium Armour, Heavy Armour

Full sets of light, medium, and heavy armour plus shields are available for levels 30, 33, 37, 40, 43, 47, 50, 53, 57, 60, 63 and 65, as well as some stronger endgame level 65 items from the Light Armour, Medium Armour, and Heavy Armour Vendor. Warden shields are classified as Medium shields. These items are about as strong as quest items of the same level. At each level band, there are a few "Veteran" items. These cost additional Marks and have better stats than the others at the same level band.

Jewellery and Cloaks

Same as Armour, but Jewelry and Cloaks!

Weapons

Similar to Armour, but weapons!

Legendary Items

Min level 65 Unidentified Legendary Items (but no main-hand weapons), runics, IXP runes, scrolls, and various other goodies.

Crafting

Scroll cases, optional ingredients, and some new special components being introduced with Siege of Mirkwood.

Scroll cases: Each holds a purple-quality one-time-use recipe. Ex: Journeyman Weaponsmith Scroll Case

• Beginning with tier 2, there is a specific one for every tier in every crafting profession.
• You do not know which specific recipe you will receive without opening it.

Shards: A special component required by many crit recipes which result in a stronger version than a regular recipe.

• Beginning with tier 2, there is one for each tier. They are not specific to any one crafting profession.

Optional ingredients: Used to increase critical chance of a recipe.

• There is a specific one for every tier in every crafting profession.
  
• only available for crafting professions.
• NOTE: criticals are only possible once you have mastered a tier.

Expertise recipes: Allow you to gain a large amount of experience -- once every 3 days

• There is a specific one for every tier in every crafting profession
  
• They require their own special components, which are also purchased with skirmish marks
• They don't require any metal, wood, hide, crops, etc. to make, allowing you to save those for once you've mastered the tier

Expertise tokens: Consumed by the expertise recipes

• NOTE: They are unusable without a recipe
• They are specific to tiers, but not professions.

Bulk recipes: Used to process large amounts of raw materials

• Available for the gathering professions (forester, prospector and farmer)
  
• They save you time but unlike regular processing do not have the possibility of generating crits (more finished resources than you otherwise would have received).

Cosmetics

Housing, cosmetic items and soldier cosmetic traits.

Provisions

The Provisioner will allow you to sell and repair items as well as purchase various potions with SM.

Skirmish Exchange

Reputation items, various items for class quests, and Mark upgrades. Basically, he's got all the weird stuff that didn’t fit anywhere else and a number of goodies you didn’t expect to see again.

Classic

The Classic skirmish vendor trades unique skirmish tokens gained as a result of doing Classic quests (and the Challenge mode in a Classic instance) for rewards that dropped from those instances before they became Classic instances. These rewards also allow access to 2nd age weapons and level 65 versions of the Annúminas and Helegrod sets with updated art and Radiance as well as a new level 30 set for the Great Barrow.