There are tons of tutorials on the forum... just have to search...
The classic air cannon style (which I use a little different variation)
tutorials-and-step-by-step/96417-air-cannons-dummies.html?highlight=Cannonhttp://www.halloweenforum.com/tutorials-and-step-by-step/96417-air-cannons-dummies.html?highlight=Cannon
There is always just pump fog through a tube:
http://www.instructables.com/id/Halloween-Pirate-Cannon-and-fog-machine-disguiser/
Mine uses a combination of both... I pump fog into the cannon tube via a old vacuum hose and then use the air cannon to shoot it out.
Found the shopping list for this as well... (total cost a year or 2 ago was a little over $20)
1 - 12" length of 2" galvanized pipe
1 - 2" galvanized pipe end cap
1 - 1/2" to 2" galvanized pipe reducer
1 - 1/2" to 1 11/2" galvanized pipe reducer
1 - female hose to FIP swivel fitting 3/4" x 1/2"
1 - lawn hose end cap
3 - 1/2" short threaded nopple
1 - 1/2" galvanized reducer bushing
1 - 1/4" IID male air coupler
1 - 6' extension cord
2 - 1/4" femail quick slide, 18ga. crip cord fittings
1 - washing machine water valve (or Lawn Gene 1" jar top anti-siphon sprinkler valve)
Here is the original pic I followed too:
The classic air cannon style (which I use a little different variation)
tutorials-and-step-by-step/96417-air-cannons-dummies.html?highlight=Cannonhttp://www.halloweenforum.com/tutorials-and-step-by-step/96417-air-cannons-dummies.html?highlight=Cannon
There is always just pump fog through a tube:
http://www.instructables.com/id/Halloween-Pirate-Cannon-and-fog-machine-disguiser/
Mine uses a combination of both... I pump fog into the cannon tube via a old vacuum hose and then use the air cannon to shoot it out.

Found the shopping list for this as well... (total cost a year or 2 ago was a little over $20)
1 - 12" length of 2" galvanized pipe
1 - 2" galvanized pipe end cap
1 - 1/2" to 2" galvanized pipe reducer
1 - 1/2" to 1 11/2" galvanized pipe reducer
1 - female hose to FIP swivel fitting 3/4" x 1/2"
1 - lawn hose end cap
3 - 1/2" short threaded nopple
1 - 1/2" galvanized reducer bushing
1 - 1/4" IID male air coupler
1 - 6' extension cord
2 - 1/4" femail quick slide, 18ga. crip cord fittings
1 - washing machine water valve (or Lawn Gene 1" jar top anti-siphon sprinkler valve)
Here is the original pic I followed too:
