What are the differences in mountain bike hubs (With wheelset recommendation)? I'm possibly getting a disc brake, 2013 Specialized Camber 29er without the wheelset. I was looking on wheelbuilder to see how much a wheelset might be (to save weight over factory replacement), and I'm a little confused by the different types of hubs available. They have ISO, center pull, straight pull center lock, and then various different brand versions.

I will be doing a lot of trail riding, with some racing (Barnburner 104, Whisky 50), so enduro/cross country/marathon, primarily more towards the marathon side. I'm not big into downhill and extreme technical.

What type of wheelset should I be looking at, and how does that affect the hub that I choose?
I would look at wheelsets that are for your specific riding style. if you're looking to choose a full wheelset from a specific manufacturer (e.g. Mavic) that includes all of hub/rim/spokes and even tire, then go to their websites for more information. These are generally lighter than a normal wheel that you can build up yourself. If you want to build up one yourself, first find a hub that fits your bike. MTN hubs come in various types based on quick release, so check what type of quick release your bike has and then look for hubs that match. as for your question on hub types, here's a quick guide:

ISO: 32 or 36 holes made for wheels that are laced 3 cross. they have a 6-bolt pattern for the disc. see here: https://chrisking.com/hubs/hbs_ISO_disc
in some instances, these hubs can be laced without crossing spokes, but you run a higher risk of hub failure. 

Straight(center) pull: this means that the spokes don't cross one another. in other words, they extend straight out from the hub. This lessens weight, but is generally avoided because they place more tension on the rims and aren't as stiff. there are also wheels that will have one side 2/3 cross and one side straight pull. These are for rear wheels and front disc wheels and lessen weight while keeping stiffness on the side with the disc. 

Straight Pull center lock: see above for info on spokes. the only difference is that instead of having a six-bolt pattern for the disc mount, they have a shimano center lock disc mount. the advantage of center lock is that they are easier to install (6 individual bolts vs. 1 lockring) which allows them to have smaller hub flanges. The advantage of smaller hub flanges is that wheels are more comfortable to ride (If you've ever ridden a purpose built track bike over potholes, you may know the feeling). 

if you have a set of rotors, check what style they are(6-bolt or center-lock) and choose hubs based on those. if you don't have rotors, find the set of brakes you have on the bike, or the brakes that you want on the bike, and determine based on that. 

once you have the hubs, choose the rims:
rims come in various styles and sizes based on your riding style. first thing is to check the size of the rim. some models only come in one size (26", 27.5"/650B, 29'er) generally wider equals heavier and more aggressive. most companies that sell rims sell them based on riding style. make sure that the number of holes on the rim matches what you have on your hub. 

after that you can choose the spokes and nipples. if you are using standard 32/36 hole rims, and ISO hubs, then just about any standard LBS will have spokes for your wheel. You can reduce weight by getting spokes that are butted/double butted/triple butted, but they are far more expensive. If you get specially designed rims or hubs, you generally need to get spokes that match that rim type. higher end hubs/rims generally require this. 

based on your question it isn't clear whether you are against getting a full single-manufacturer wheelset, but I hope this clears some things up and helps you get the right wheels.