Lists of eight letter words for Scrabble are available on BestWordList.com and AllScrabbleWords.com, as of April 2015. The list on AllScrabbleWords.com includes words that can be used in Words With Friends or Text Twist, so certain words may not be possible with the tile distribution used in Scrabble.
Visit the BestWordList.com homepage, and click on 8 under the Lists of all words heading. Words are listed alphabetically and shaded either red or green. Red shading indicates the words are found in the SOWPOD word list, and green shading indicates the words are found in the SOWPOD and TWL06 word lists.
Visit the AllScrabbleWords.com home page, and click on 8 Letter Words under the Unscrambled Words By Length heading. Words are listed alphabetically. The website also has an unscrambler tool that allows you to enter up to 12 letters and determine all possible words for those letters.
There are multiple Scrabble word lists available, and a word list is typically chosen before the game. That word list is consulted if there are any challenges. A challenge occurs when an opponent claims that a player used an invalid word. If the challenger is correct, the word is removed and the player who used the invalid word loses his turn. The penalty for an incorrect challenge varies, but common penalties include the challenger losing his turn or losing a certain amount of points.