Remember when Air Wick first brought out their Stick Up air fresheners, and their tagline was "this is a good place for a Stick Up." Clever. I remembered it just now after more years than I care to remember. They're not terribly expensive (I just checked on amazon.com, and they run less than $2 for a 2-pack), until you realize that they're nothing more than some fragrance and maybe some baking soda.
Here's my super-cheap way to keep your smelly kitchen (or bathroom) garbage can under control: sprinkle plain old baking soda liberally on the bottom of the garbage can itself (not inside the bag). I cover the bottom of my can completely with a thin layer. It absorbs odors exceptionally well, and lasts a long time (several months, if not longer, depending on the thickness of the layer. Switch it out when it starts not doing its job (trust me, you'll know when it's time).
Not only are you saving money, this is easy on the ol' landfill, too, as you aren't having to toss little plastic containers.
