iKnowthat.com has multimedia educational games for kids ages 2-12.

Alien Word Mine Game

This is an arcade-style game in which kids learn about nouns, verbs, pronouns, adjectives, adverbs, and other parts of speech.  Other topics include contractions, synonyms and antonyms.  There are different vocabulary sets for primary elementary grades and intermediate elementary grades.

In this language arts game, kids use parts of speech to sort words.  As they move to higher rounds, kids have to collect more words.