When shots are shown of the group playing poker, a space is left between Phoebe and Chandler to allow room for the camera. However, when a bird's eye view is shot, the group is equally spaced around the table.
When Joey is getting coffee off Rachel the mug is blue, when the camera switches the mug becomes yellow.
When Chandler jokes about settling the Jamestown Colony of Virginia, he says "King George is giving us the land." Jamestown was settled in 1607 during the reign of James I (hence the name Jamestown). Chandler seems to be confusing the date of the Jamestown settlement with the American Revolution (during which George III was king).
When Ross and Rachel are squaring off at the end, Rachel wins with Ross giving the appearance that he's thrown in his hand without revealing his cards. Joey and Chandler scramble to look at his hand as Ross tries to prevent them from doing so. However, moments before, Chandler and Joey are standing right behind Ross and clearly see what cards he has. Therefore, they would have known what cards Ross had.
In the final game, each player starts out with 5 red and blue chips and 10 white. The final pot has too many chips, at least of the red and blue kinds.
When Phoebe asks for a ten of spades Rachel offers hers but hands her a ten of hearts instead.