One thing to remember is that the work permit option could take awhile - you have to find an employer willing to sponsor you and they have to get what's referred to as "HSRDC approval" to offer you a job. What that means is that they have to show the government that there are no qualified Canadian citizen/PR candidates for the position. If they get HSRDC approval, then they can offer you the job and you can take that job offer, along with an application for a work permit and the accompanying fees, to a Canadian port of entry to try to get a work permit. (BTW - US citizens ARE allowed to apply for a work or study permit at the border, but some IOs will tell you that you have to go to a Canadian consulate in the States to accomplish this. So be prepared for a possible hassle.)
Other than that, the fastest route to permanent status in Canada (which gives you the right to work) is being sponsored by a spouse or common-law partner. I agree that it's not wise to jump into marriage, especially just to facilitate coming to Canada, but don't make the mistake of trying to come to Canada as a visitor for six months with the idea of extending that visit for another six months to qualify as a common-law partner. First of all, that goes against the intent of the six month "rule", and secondly, it only puts you in a position of not being able to work legally for the entire first year - and then again for however long it takes you to finally get the PR application approved . . . which is a minimum of six months - and could be much longer (up to 2 years) if you make the mistake (as a US citizen) and file inland.
Anyway - I'm probably getting way ahead of you on this, but just for information's sake, take a look at the
US2Canada website and you'll get a better idea of what's involved in the sponsorship process.