A typical pair of 6-sided dice 
JabberWokky's chest of roleplaying dice. Dice bags are also common.
Dice are for sale at Alphabet Moon, Bizarro world, and most drug stores.
Dice are most commonly used in Games but the uses don't stop there. Here are a few things that are done with dice:
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Roleplaying games are usually played with a variety of 4, 6, 8, 10, 12, 20, 30 and 100-sided dice. Dice with other amounts of sides can be found, but are usually fairly rare, while those are commonly used and available. 2 sided dice are affectionately referred to as "coins", although there are 6 sided dice with 3 faces labeled "EVEN" and 3 labeled "ODD" for many games. The various sides are referred to as "d", so a 20 sided die is a d20. d100 often refers to two d10s, either with distinct colors or one as a "percentile die", with the faces labeled 00, 10, 20, 30, etc. Rolling both and adding them together gives a result from 1 to 100. Actually 100 sided dice look more like over-sized, awkward golf balls than dice.
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Novelty dice with things like pizza toppings on them so you can roll your order.
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Adult dice with various positions and actions are available from Evangeline's in Old Sacramento and many places that sell Sex Toys.
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Some drinking games are played with dice.
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People may also engage in gambling with dice.
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You could also make a decision with dice, if you are indecisive.
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Some people like to hang them from rear-view mirrors in cars. Preferably after they've grown fuzzy.
If you're feeling destructive, you can make your own huge dice out of The Dominoes statue.
