novaderrik is right about there being loads of related work, since the population is exploding. So, they need builders, electricians, welders, retail, food service, health care, etc. Basically, everything that relates to growing communities of humans.
But, keep in mind that the cost of living has exploded as well, particularly housing. So, your $15/hr flipping burgers will not go as far as it once did.
Oil field work is pretty brutal, just search YouTube for some videos and you'll see what I mean. Good way to get an arm ripped off if you're not careful. But hey, if that's what your into, why not give it a shot. The Bakken will have a long run (decades even), so there's plenty of time to get experience and make your money.
Truck drivers, particularly those with Class A and Hazmat certs are in huge demand. They have to truck water to the frack site, oil and waste water away, as well as well casing, piping, and other equipment and supplies. Trucks are pounding the roads up here, 24/7.
If you can find a job and housing (often they go hand in hand) before you come up, you'll be miles ahead of most folks. But, as others have said, that's not always that easy to do. Totally worth some effort though. And, whatever you can learn about the jobs and the fracking process the better.
I set up a page here (http://www.bakkendispatch.com/north-dakota-oil-job-resources) with some links to useful job sites. Check out the jobsnd.com site, as that's the official state site, and pretty good. But check wherever you can, even if you just find a temp job to pay the bills while you look for something longer term.
Good luck to all. Follow that boom, if that's your thing.