hi

i am in a bit of a situation. i have been here in th us for over 5 yrs. i lost my passport and got a new one, i also had to get a new I-94 to renew my drivers licence.

now i have to go to canada to attend a meeting and this in important for me as i am about to graduate and i need to find job. 

here's the situation. i have new passport but no visa sticker. i have valid I20 vaild till july 2013 i have I94 re-issued.
now, can i go to canada and return back to us or do i have to have an american visa to come back.? and secondly can i apply visa while in canada? 

i have read people stamping visa in canada. 
i'd really appreciate if you share your experience.

thanks in advance