I recommend Vocabulary.com and I guarantee that you will learn words and have fun at the same time.
The site offers FREE, kindergarten-adult interactive puzzle activities. This self-paced site, based on state standards, has PRINTABLE lesson plans and exercises. All content is original and supplemental to school curriculum with time-saving activities as helpful reinforcement for teachers, students, and parents.
Jane Strauss, author of The Blue Book of Grammar and Punctuation and the website www.grammarbook.com