Dominoes are tiles with a number of spots at each end. Originally, each domino represented a throw of two dice, so each end of the domino has from one to six spots, giving 21 possibilities in all. (In general, if there are x different possibilities for the end of a domino, the number of different dominoes is x*(x+1)/2).
European (and American) sets of dominoes also include tiles which are blank (zero spots) at one or both ends. A normal (so called double six) set of Western dominoes has one of each possible tile, and therefore contains 28 tiles. Larger sets are also found. The double nine set (from zero to nine spots on each end, 55 tiles) is common in the north of England and in North America. In America double twelve sets (91 tiles) are also found, and some double fifteen sets (136 tiles) have recently become available.
Here are Joe Celko's pages on Games played with Western Dominoes.
Western dominoes are traditionally used for games in which the tiles are played to a layout, matching an end of each new tile played to one of the free ends of the existing layout. Layout games with dominoes include the Draw Game, the Block Game, the Fives Family (including Muggins, All Fives, Five Up and Fives and Threes), Matador, Caribbean Dominoes, Bergen, Flower and Scorpion, Train, Chicken Foot and Nos.
In some parts of Europe and North America, there are also a few games in which the dominoes are played like cards rather than used to build a layout, Some of these are games specially devised for dominoes (such as Texas 42 and Moon); others are direct adaptations of cards games, such as domino cribbage and domino whist.
Dominoes originated in China, and Chinese dominoes are still used in China, in Mongolia and in places with Chinese communities. Chinese dominoes can be recognised from the fact that
The duplicated dominoes are 6-6, 1-1, 4-4, 3-1, 5-5, 3-3, 2-2, 6-5, 6-4, 6-1, 5-1, and in some games they rank in that order from high to low. The unique dominoes are 6-3, 5-4, 6-2, 5-3, 5-2, 4-3, 4-2, 4-1, 3-2, 2-1. Eight of these are grouped into pairs having 9, 8, 7 and 5 spots. The remaining two (4-2 and 2-1) also form a pair which in some games counts as the highest of all, beating a pair of double sixes.
Here are Joe Celko's pages on Games played with Chinese Dominoes.
Chinese domino games are seldom of the type where a layout is built. The dominoes are used like cards, for games belonging to a variety of card game families. For example Pai Gow is a banking game, Tien Gow is a trick taking game, Tiu U is a fishing game and Kap Tai Shap is a rummy-like game. In Tibet, the trick-taking game Bagchen is played with a double set of 64 Chinese dominoes.
In China, dominoes also exist in the form of long narrow cards with the value of the domino on each end. These come in packs of 32 for Tien Gow and also in packs of 84 (with four of each possible card) for Chang Pai or Shiwu Hu Pai.
Andrew Smith has provided a PDF file of 21 domino cards which could be used to make your own pack.
The Domino Plaza site has a good collection of information about games played with dominoes.
Randy Rasa's Domino-Games.com site offers a comprehensive listing of domino software for Windows, Macintosh, PocketPC, PalmOS, and of places to play dominoes online, as well as information on domino rules and history, and a listing of online sources for buying dominoes.