Can anything be done about a slow leaky tire?

[SzczerbiakManiac]

One of the tires on my car has a slow leak and I need to add air about every 10 days. Is there something cheap I can do to fix it or am I gonna have to get new tires? I've heard there is some kind of aerosol you can squirt into the tire that coats the inside and effectively plugs the leak, but I don't know if they really work or if there are other issues associated with them.