The most intrusive of un-pleasantries: bad smells. HowToGetRidOfStuff.com have a couple of tutorials on getting rid of some of the worst.
First we have cleaning cat urine out of both carpet and upholstery using not much more than Water, White Vinegar, Baking Soda and Hydrogen Peroxide.
Second is just about every way to get rid of cigarette smell from almost anything; walls, furniture, clothes and, in this example, the car:
Fill a tub with vinegar and place it on the floor in the front seat, close the windows, open the floor vents and turn on the heat full blast. Let the car run in this state for an hour before removing the tub. Another version of this remedy requires hot summer weather and allowing the tub sit on the floor with the windows closed all day.
Lastly there is shoe odor prevention and removal. They cover how to stop your feet stinking up the place when you kick up your heels and how to ease the smells when they do.