For great looking fog, you no longer need to go to the local film prop store or Halloween store (which is almost always closed 11 months of the year). You can make your own homemade version of a fog machine.
Okay, it's not as strong as a electric-powered fog machine, but if you need to save money, and can't find once anywhere else, then dry ice is the answer.
Kipkay shares the instructions for making this might, miniature fog maker. For dry ice, it sure does produce some foggy results (foggy not meant in a bad way).
You will need an empty coffee can, a computer fan, marker, knife, hot glue (or other epoxy), 9V battery clip, 9V volt battery, pool hose, sheers, mini grinder, and of course…. dry ice.