The past couples of days I was home sick, so I searched the Internet for some activities my class can do with a relief teacher. I stumbled across a free online crossword puzzle maker (http://www.crosswordpuzzlegames.com) . I gave the students a list of words (relating to the topic) and they had to define each word in order to make the crossword. I gave them 30 min to complete the task. All crosswords needed to be printed in pdf (electronic) and emailed to me for checking. Very easy to use and the students enjoyed the task. When I returned, I gave the students random crosswords to complete and we discussed some definitions. Walla!
The site also has other puzzle games.