There are many different forms of poker that are played in cellars, dens and kitchen tables throughout the poker world. They often include wild cards, changing wild cards, being able to buy extra cards, redraws, matching the pot if you lose, and other interesting twists. I've assembled the rules to many of them, grouping them by the game they most resemble (5 or 7 card stud and draw poker):

5 Card Stud:
In 5 Card Stud, players each recieve five cards. Being Stud poker, there are no redraws, and the cards are placed on the table. The first card each player recieves is face down, the the second, and al subsequent cards being placed face-up.
There are several rounds of betting in this game, beginning after each player has received their first two cards.
The player with the highest hand at the showdown wins the pot.

7 Card Stud:
Seven Stud is played in basically the same way as five card stud. Players each receive two down cards and one up card. A round of betting takes place. Then a fourth card is dealt face up, followed by a round of betting. A fifth card is dealt face up, follwed by antoher betting round. A sixth card is dealt face up, followed by more betting. Then a final seventh card is dealt face down.
The final round of betting takes place. Players make the best five card hand they can from the seven cards they've been dealt. The highest hand at the showdown wins the pot.
Seven Stud can be played as a hi/lo game as well, where the pot is split between the highest hand at the table and the lowest qualifying hand.

Draw Poker:
Is the classic version of poker that we've seen in the Wild West films. It has also made it's way to the screens of video poker machines in casinos worldwide.
In this version of poker, players are dealt cards and given a chance to replace cards from their hand with a redraw. The popular version of draw poker is 5 Card Draw, which is a high hand takes the pot game. Other versions of draw poker exist, and some are even played online.