The best place to look for updated information is at www.nserc.ca
I received an undergraduate NSERC; there are others available for industry and graduate students and you should check the above web-site for more information regarding those awards.
Basically, you need to find yourself an employer, who usually ends up being a professor in your Faculty/Department. These prospective employers and yourself then jointly fill out an application form to NSERC, consisting of your personal information, an attached undergraduate transcript, and a short statement describing your employment project.
This application is then submitted to the Head of the Faculty/Department. He/she will tally up all the applications and then send the promising ones off to NSERC. After that, once you start working, NSERC starts mailing you cheques each month. This saves your employer some money, and gives him/her the incentive to hire summer students.