The most commonly used woods for BBQ are Hickory and Oak, but here's a list of all the woods you can use for smoking:

ACACIA - Tre from the same family as mesquite. When burned, acacia has a flavor similar to mesquite yet not quite as heavy.

ALDER - Delicate with a touch of sweetness. The traditional wood used for smoking salmon by natives of the Pacific Northwest. Good for fish, pork and poultry.

ALMOND - A sweet smokey flavor. Good for all meats.

APPLE - Quite mild with a slightly fruity flavor. Good with poultry and pork.

ASH - Fast burning, light distinctive flavor. Fish and red meats.

BIRCH - Flavor similar to maple. Pork and poultry.

CHERRY - Mild, fruity. Good with poultry, pork and beef.

COTTONWOOD - Softer wood than alder. Very subtle flavor. Don't use green cottonwood.

CRABAPPLE - Like apple wood.

GRAPEVINES - Tart and rich. Lots of smoke. Poultry, red meats, and lamb.

HICKORY - The King of smoking woods. Sweet, strong, heavy bacon flavor. Pork, ham and beef.

MAPLE - Mellow and slightly sweet. Pork, poultry, cheese, small game birds.

MESQUITE - Burns very hot. Sharp earthy flavor. Beef, fish, chicken, and game.

MULBERRY - Smells sweet and apple-like.

OAK - Heavy, assertive smoke flavor. Best with red meat, pork, fish. Unbelievable with beef brisket.

ORANGE and LEMON - Mild smoky flavor. Perfect for beef, pork, fish and poultry.

PEAR - Gives subtle smokey flavor. Chicken and pork.

PECAN - Sweet, mild and similar to hickory but mellower. Burns cool. Poultry, beef, pork and cheese.

WALNUT - Heavy smoke flavor. Best mixed with lighter almond, pear or apple. Red meats and game.

Other good woods to experiment with include BAY, CARROTWOOD, KIAWE, MADRONE, MANZANITA, GUAVA, BEECH, BUTTERNUT, FIG, GUM, CHESTNUT, HACKBERRY, PIMIENTO, PERSIMMON