Best thing to do is to vacuum seal it. Whenever I get a really good strain I like to put away a few grams for a later date. I get out the FoodSaver and seal it up. I recently opened up some white widow that I've had for almost two years and it was practically as good as the day I got it.

I've heard that freezing is actually bad for weed. The freezer can dry it out (thing freezer burn) and damage the trichs. Don't know if it's true or not though.