Supplement your traditional textbooks with Discovery Digital Textbooks. Discovery Education is offering educators throughout America a freetrial to use its Techbook™ service through the end of June. I looked into it and they have some really good stuff for Science and Social Studies. Give it a whirl, it's well done and free for now!
"Students can fly, swim, feed, and toss their way to grammar mastery.
Characters can be led through many adventures as they practice using
nouns, verbs, adjectives, and more; a quick and easy way to practice and
reinforce different grammar concepts to enhance reading, writing, and
parts of speech."
Grammar Wonderland is available in two versions: k-2 and 3-6