http://www.cic.gc.ca/english/work/index.html
For work permit application, vist
http://www.cic.gc.ca/english/applications/work.html
Basically, you need offer letter, HRDC confirmation and your bank statement. The HRDC confirmation may take 3-4 months after your position is filed by your employer. The work permit and visa application in Canadian embassy or consulate will take two weeks. If approved, you will get an approved letter for work permit and a tempprary resident visa (TRV). The work permit will be issued at the port-of-entry when you get into Canada. If you have been in US for more than 6 months, you don't need medical exam.