Assuming you DON'T have your parents' consent, a couple rolls of duct tape around the seams of whatever they're growing in works wonders. You just have to watch out for when you open the fucker up again cuz the smell will be concentrated. You can probably also duct tape yourself in there and get high off the fumes. I know that the fumes from bud make me get stoned!
There are odor blocks you can buy for like 7 bucks each. Get a few of those and they cancel out the odor molecules. Aparently that is, ive never used them.
I bought a little charcoal filter/fan contrapshon(spelled wrong) from home depot, if ur in the u.s for 13$ i have 6 plants and it keeps the room fairly fresh although i would like another one, you can catch a wiff here and there
I use ONA. They work wonders for "masking" odors ... amazing stuff. You should still use charcoal to remove odors, but for masking odors ONA is great. http://www.plantitearth.com/store/product.asp?id=145&catid=54 Good Luck!
those are just masks...they cover the smell with another most use carbon filters or vent to the roof you can also consider the strain Fruitbowl = very low odor Haze Skunk = very low odor