Merriam-Webster’s Word Central

Word Central gives students a quick word lookup for dictionary meaning, thesaurus, and rhyming words.  There are other interactive tools here.  Students can add to a student-created dictionary, which can be browsed alphabetically.  Word Central guides them through adding a word, and all the parts of a dictionary entry that go along with it.  There’s a daily “buzz” word, and a few vocabulary building games, aimed mainly at middle and high school age students.