There are some problems that role-playing can handle well on it's own. Sometimes combat may be necessary, depending on what system you're playing (as well as the GM). It's not very often that instead of going for their guns or blades NPCs can grab a deck of cards or a pair of dice. Games of chance lend themselves very well to an ongoing campaign. Cash and barter come easily to mind but there's also the purposes of information and side quests.
I'm not promoting dangerous gambling here. I've been lucky enough to lose less than one hundred dollars in my life with all the games of chance I've played. Real assets should only be wagered in the amount they are in excess of one's bills and never as a means to meet those bills. However when the assets are imaginary there's a lot of fun to be had with chance. Most everyone is familiar with poker, blackjack and craps. These are simple games you can use to fill your taverns with people as low-level PCs try to get enough cash for a nice set of armor or high-level PCs run a business establishment. Once I let a player gamble to get enough horses for her and her adventuring party to cross the grasslands more quickly. She offered to pay but that NPC was more interested in playing a card game I call "bad suit." More on that later!
Among traditional scenes I hold dearly is the lone traveler entering a tavern, having to play cards in order to speak with someone. It intrigues me when players are forced to speak someone else's language in order to gain information. This is a lot more entertaining than simply bribing a person with cash. Everyone has things which impress them. Bringing in characters who are only impressed by people with skill or luck adds flavor to the game and is a wonderful reprieve from run-of-the-mill information gathering ventures.
Games of chance can also tie together barter and information. While I don't recommend making the only way to get a crucial item through a game of chance it is a great way to enhance character's abilities beyond what they otherwise would be. In other words, the key to the final door in the final dungeon shouldn't be up for betting on the bad suit table – but the map to the most powerful ship in the waters might be. If games of chance are common in your game then there might even be variant rules from region to region. My example for winning horses in a card game tied to bonus quests later down the road. Once that player got good with games of chance I planned on letting her use that skill to win some really good equipment down the road. Even though games such as poker and bad suit are largely chance there is still some amount of skill involved.
Now for "bad suit." Here are the rules:
• Using a standard deck of cards (without jokers), every player begins the game with five. Bets are placed when the hands are first dealt.
• Keep going around the table until everyone has either put in the same amount of wealth (a horse, gold or the like) or has gone all in. One person going all in doesn't mean everyone else needs to; They only have to meet the amount to stay in.
• Your NPCs shouldn't give any information here; Instead hint at what knowledge they might have if the players raise their bets.
• After all bets are placed everyone left in selects two cards to drop from their hands. The goal is to have the sum of the remaining three cards be as high as possible.
• When everyone has a hand of three cards the dealer turns over the top card of the deck. Any cards that match the drawn suit (the "bad suit") have their effective value dropped to zero.
• Winner takes all. Ties are resolved by dealing new hands in a no-betting sudden death.
• Depending on the difficulty of your game and the level with which you wish to involve games of chance, the NPC can reveal their knowledge after one loss or a few consecutive losses.
Games of chance can really flesh out your campaign and bring a nice break to players who are bored of combat or other forms of mechanical diplomacy. Brush off that poker face and liven up your game world with some uncertainty. Happy risking!
Video of bad suit: http://youtu.be/UqOqyHV51wY