In the other dryer heat recovery thread, the most reasonable reply I saw was to question why anyone would ever use a dryer. Piwoslaw had a photo of how it is done in Poland, in a room (hopefully sunny) where the clothes air dry.
From what I understand, Europeans don't like dryers, partly because of energy costs, but even more because the dryer shortens the life of clothes... that's what all the lint is about... it is damage to the clothes that have been dried.
If you can successfully vent a gas dryer (which is releasing very large amounts of CO2) inside the house, it means that your house has a very serious infiltration problem. Releases of CO2 that large should cause a loss of consciousness in a well-sealed house. Any savings you realize through dryer heat salvage is being off-set 24/7 by massive infiltration. You'd be much better off dumping the heat and focusing on the infiltration leaks.
But if you are a slave to the dryer and really don't care about shortened clothes life, there is still hope...
there is a type of dryer that doesn't need a vent at all, it uses the principle of a dehumidifier. It is more power efficient than resistance heat. you get to keep all the heat and lint and water (which you will need to provide a drain for).
-AC