Jimpa and Tapas77,
If you get a job in Canada with a US based company (there are hundreds of US based companies having operations in Canada), then you can file form N-470 to obtain permission from USCIS before you travel out of US. This link has some useful info and tips on how to maintain your US GC while being out of US.
http://www.immihelp.com/greencard/retain-greencard.html
