I was reading a book about the space race, and it mentioned that polar orbit was more difficult to get into and the Van Allen radiation belts were more prevelent. I tried serching on the internet, but was unable to find any information if a human had ever been in polar orbit? So the question is, has a human ever been in polar orbit?
Ben
Nope.
If you look around you can probably dig up a list of the orbital inclination of the various manned (and womanned :)) space flights to find out what the closest to polar orbit was. Most of the US missions (before the International Space Station) were of a lower inclination than the Russian flights because the Russian launch complex is farther north of the equator. ISS was put into an orbit who’s inclination allows launches from both the US and Russian space centers.
When the Space Shuttle was developed, Construction was started on a facility at Vandenburg Air Force Base in California that would allow it to be launched into a polar orbit. They didn’t want to launch into polar orbit from Florida because it would need to fly over populated areas on the way up.
The Air Force wanted the ability to launch a military shuttle flight into polar orbit, pass over Russia and land after a single orbit. Eventually the plan was shelved and the launch facility was never completed.
Eric
Your question was asked in a Question of the Day at Spacetoday.org. Unfortunately, they don’t answer the question directly, so I will. The answer is no.
The US space program uses two primary launch complexes:
Kennedy Space Center: equatorial
Vandenberg AFB: polar/elliptical
The Russians also have two (active) primary facilities:
Baikonur Cosmodrome: equatorial
Plesetsk Cosmodrome: polar/elliptical
Inserting a satellite into an equatorial orbit requires less energy and allows for more massive payloads than a comparable launch into polar orbit. It’s cheaper to launch the heavier manned missions from KSC or Baikonur. It’s not impossible to launch people into polar orbit - there just isn’t a good reason to spend the extra money to do so. Most man-made objects in polar orbit are Earth-sensing or reconnaisance satellites that take advantage of greater ground coverage and a constant angle of the sun. One other factor worth considering is that for the space shuttle, safety considerations require a launch over ocean in the event of a “catastrophic failure”. We wouldn’t want a vehicle to explode or crash over heavily populated congressional districts, would we?
As to radiation … yes there is more radiation, but not enough to be a problem.
There have been plans to put people into polar orbits in the past, but none have succeeded (to the best of my recollection). 
A shuttle facility was proposed for Vandenberg from the beginning of the program. This design specification was one of the primary reasons for the unpowered landings (couldn’t afford the extra mass of engines and fuel). It is unlikely to go forward. Gemini B was designed for polar flight, but never saw a manned mission. Also, some elements of the Apollo program were planned with polar orbits in mind but ended up in Skylab. If anyone had a reason to do it, it would be the Russians. Equatorial orbits aren’t very good for observing their homeland. Unfortunately, I can’t find any evidence of a manned mission in a polar orbit. Soyuz vehicles are lanuched from Baikonur.
Just to give people an idea of the payload reduction needed:
An STS going into a standard orbit (i.e., launching due east from Cape Canaveral) has a payload limit of 25 000 kg. (The heaviest payload actually carried on an STS was the Chandra X-ray telescope, tipping the scales at 22 680 kg.) If an STS were launched into a polar orbit, the payload limit would be somewhat lower than 10,000 kg. So gram for gram, it’s more than twice as expensive (for the US) to launch humans into polar orbit (not even adding the expense of maintaining Vandenberg as a launch site).
So that’s where she is! Someone let the DCPD know! 
[Standing to give polite applause]
Excellent answers. I am once again reminded of the invaluable resource that we are blessed with in The Straight Dope.