Today I came across It's A Mad Libs World!...Online Mad Libs. Cool! The kids fill out a form that asks for parts of speech, click "submit" and the story appears. If they forget the definition for one of the parts of speech, they just mouse over the term and a definition pops up along with a few examples. There are 13 Mad Libs categories to choose from. Our favorite is Pirate Mad Libs!
Mad Libs not only reinforce simple grammar, but they're great for reading practice, too.
Check it out. It's a fun site!