Here's something I found on a google search. There are some references listed as well:
http://www.ascd.org/publications/ed...m01/Five-Hallmarks-of-Good-Homework.aspx"In an effort to create appealing tasks, teachers sometimes compromise learning. A word search may look like fun, but it has little value in reinforcing spelling and can be a torturous task. A better task would be for students to create their own pattern of content-related words, as in Scrabble. Likewise, crossword puzzles are fun, but students may benefit little from matching definitions with words when the focus is on solving the puzzle. A better task would be for the students to find connections between the concepts that the words represent. For example, students might group words as "feeling words" or "action words," as nouns or verbs, or as words with one or two syllables."