Partial List of AR-15, 308AR and some alternate caliber AR Barrel manufacturers

Excellent Barrels Select one of these barrels if you plan on shooting from benchrest or prone supported, accuracy is essential and you use quality ammo.
Bartlein Barrels Truly Quality barrels, used by GAP. However to AR'erize one you need to buy the barrel and have it chambered by another company.
Lilja Top quality barrels, often have 7.62, .223wylde and .204ruger in stock. Any length above 16" and many calibers available.
Krieger Top quality barrels in any caliber and any plus 16" length
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Great Barrels Select one of these barrels if you care about accuracy and shoot a variety of ranges, positions and courses of fire
JP Rifles .204, .223wylde,  6.5 Grendel, .308, .260 and .338 in 14.5" and up. Barrel price starts at $400.  BEST GENERAL PURPOSE
Lothar-Walther Some great barrels in .223Wylde, Rem, and 5.56 Nato. Custom barrels in 7.62
Hart AR Ready barrel up to 30in,$460 in 416 stainless.  Awesome fluting options. Will headspace your bolt
Douglas AR barrels can be baught from CLE
Shilen AR Ready in 20 and 24" in .204, .223Wydle and Match and 6.8. 
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Very Good Barrels Select one of these if you shoot a fair percentage of your rounds at 100 and closer, but still want to be able to shoot well beyond that with accuracy
Noveske Great barrels.  .223 Mod 0(similar chamber to Wylde), 7.62,  6.8 and 300AAC.  7.5" to 20" lengths. The price jumps significantly with every inch.
Rainier Arms .223 Wylde in 10.5" to 20". 300AAC, 6.8, .308WIN in 3 grades of barrel, all great value. 
Wilson combat Nice Barrels, 5.56Nato, .223Wylde, .204 Ruger, 6.8 SPC II, 300AAC, 7.62x40WT
   
Military Grade Barrels You run your AR like the weapon it is and was designed to be. You just want to kill zombies with a variety of ammo
Bravo Company Famous value, quality and customer service.
Daniel Defence A very nice barrel
Lewis Machine and Tool Long lasting, quality barrels
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AR-erizing  
Compass lake (CLE) They do their own .22 and .223 barrels and they finish (AR-erize) for Douglass, Kreiger, Bartletin or anyone you want.
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Barrel brands for cheap builds, brands I have not used and brands you may not know
Green mountain barrel 5.56 Barrels as low as $139
Montana Rifleman Many lenghts, twists, calibers and barrel alloys available. 
Criterion Barrels Available from CLE
Pac Nor When you click their AR barrels link, it goes straight to Noveske's website.
Schnieder Website under construction, information is pending
Black hole weaponry Variety of barrel lengths and calibers from 7.5" to 20+. No personal experience with them
Rock Creek Barrels Custom barrels. I have had no experience with them.
Beaver Creek Armory Cheap but they may be out of buisiness
Gunquester - gunquester2@gmail.com