If you just throw the yeast in the freezer you
will kill it!
You can freeze yeast and many including myself do it successfully. I have over 7 strains in my bank and have used some that were more than 6 months old. I have some that are now a year old.
I have 20ml plastic vials. I make a solution with 10ml water, 5ml Glycerin and 5ml yeast.
You have to be VERY sanitary when doing this.
Boil and cool some water, sterilize and/or sanitize the vials and everything else that will touch the solution.
Some people work next to an alcohol lamp which creates an updraft to keep airborne contaminates away. I work next to the burner on my stove.
I get my yeast from making a starter larger than what I need for the present brew. I use a medicine syringe to measure out the glycerin, water and yeast into the vials. I make up 4 vials which if I then made 4 more for 4 generations I could brew 256 times from the initial purchase. I then chill them in the refrigerator for at least a few hours then put them in the freezer surrounded by freezer packs to counteract the defrost cycle.
Here is a link to one of the threads that got me started:
http://www.homebrewtalk.com/w.homebrewtalk.com/f13/guide-making-frozen-yeast-bank-35891/
Do a quick search and you will find many more.