One of the generators I used was Wordle. This is mainly like a free association word game, such as for brainstorming. It would be applicable particularly in language arts classes, but could also be useful in technology classes, such as a wrap-up activity to have kids write down all the terms they remember from a particular lesson.
You can see the wordle I created, which was a simple brainstorm of terms related to personal finance, over to the right, underneath the voki.
Another image generator I used was comic strip generator. I think it allows students to utilize their creativity. It would be a fun project kids could do to inject humor into a lesson. The URL where I created it, and got the picture from, is: http://www.comicstripgenerator.com/maker.asp.