BUNAC will get you a work permit if you are aged 18-30 and a full-time student at the time you apply. The work permit is good for six months.
Obtaining Canadian citizenship is a little harder, but not impossible. If you happen to have a close relative who's a Canadian citizen, she or he could sponsor you. They can only sponsor you if you're their grandparent, parent, spouse, or a child, sibling, niece, nephew, or grandchild who is under 18 AND unmarried.
Canada might also allow you to immigrate under their Skilled Worker Points system. Basically you have to have so many 'points', 67 in fact, and you show you can financially support yourself, you can get a visa. It breaks down like this:
Education -- you can get a maximum of 25 points. For example, if you've got a Bachelor's degree that gets you 20 points.
Languages -- you can get a maximum of 24 points if you speak one or both of Canada's two official languages, English and French. If English is your first and only language, that's 16 points. If you speak basic French as well as fluent English, that's an additional 4-8 points. If you speak both fluently, that's 24 points.
Work Experience -- you can get a maximum of 21 points if you're in a profession on the Skilled Worker list. Points vary depending on how many years' experience you have.
Age -- you can get a maximum of 10 points if you're in the most desired age range, 21-49. You'll get 6 points if you're 19, 2 points if you're 53, etc.
Arranged Employment -- you can get a maximum of 10 points if you have an approved job offer in Canada.
Adaptibility -- this one's tricky, you get points based on whether you have family in Canada, whether you've studied or worked in Canada, etc.
In addition, you have to show you have enough funds to support yourself, $10,168 for a single person. You have to be in good health and have no criminal convictions. I'd have about 49 points -- not quite enough, but if I got a college degree and a job offer in Canada I'd probably have enough. I would recommend checking
Canada's website on Citizenship and Immigration.