One method I use is re-circulation filtering. I used a fan inside the room, that didn't vent outside, instead took the air down a pipe, and passed it through a condensation trap that you can get for old style tumble driers. Only my trap has a lot of active carbon in it, and the air blown by the fan forces the stinky air into/onto the active carbon. The air then leaks out back into the room via holes in the trap. Can fabricate that for cheapness from parts on eBay.
Pro's: Keeps ambient room smells suppressed to a degree.
Con's: It isn't part of the air ventilation system, so need a seperate means to allow air to circulate.
You need fresh air in, and fresh air out to keep the oxygen/CO2 levels fresh. An inline carbon filter (connected to your outlet pipe from your fan, between the grow room and the outside vent) is definately easier, as combines the two together. Its a cheap build, and good for keeping the smells down, albight not eliminated. Not ideal for a full time setup, but its certainly an option if pennies are a factor at the mo.
Another option is an ionizer. You can get one for very cheap, and work throughout the house as plug-in's. Now these alone won't do much to keep your lovely ganjy smells under control, but used throughout the house they can help take care of stink leak.
Lots of options for fighting smells and air circulation. Depending on the scale of your grow, you won't automatically need some of the fancy gear the bigger growers use, just use common sense and get what you need in proportion to your levels of stinkage. Don't need to spend big to tackle the issue, a little ingenuity and pre-planning can save a lot of money.
When in doubt - window shopping on eBay for prices, options and ideas.
