The definition of a cabin can vary greatly. Is this just a small place in the woods? Does it have running water/plumbing? If it does you might have a leak somewhere that is causing the humidity. If not then it's just possible that the environment is simply quite humid.
If you already have central air than a solution like REP's would work great.
If you don't have central air than a portable air conditioner will take some humidity out of the air but a much better bet for preventing humidity and eventual mold buildup is simply a dehumidifyer.
Keep in mind that mold growth typically starts becoming a concern in environments with a sustained humidity over 60%. In general you want to aim for about 50% humidity so it's not too dry. Your first step might be to get a hygrometer and see just where you stand.
The other big concern here is that it sounds like you leave the building unoccupied for a large portion of the time. Unfortunately most dehumidifiers require you to drain the accumulated water fairly regularly (depending entirely on how humid the environment is).
Consumer search is always a good place to start when looking for appliances, they tend to be pretty honest with reviews because they look at a lot of different sites and user reviews. http://www.consumersearch.com/dehumidifier-reviews
This is all assuming you have power at your cabin. If not then we're talking a whole different story.