Since almost anything can be a mnemonic device, ask students to tell the most ridiculous story that they can think of using the vocabulary word. Make it into a contest and see who can come up with the most outrageous story. Listening to a few stories will almost certainly lock the vocabulary word into memory.
Offering challenges can be another effective way to have students memorize vocabulary words. Crossword puzzles or anything that resembles the Wheel of Fortune game show are examples of this approach. Since students will spend a lot of time thinking about these words, they may memorize them along the way.
There are many websites that offer free online vocabulary games for all ages. Some offer puzzles, word searches, and variations on hangman to name a few. The following two websites offer numerous vocabulary games: http://www.vocabulary.co.il and http://www.playkidsgames.com. These websites are especially good for parents, who want their children to do something educational on the computer.