ABCya.com is a wonderful website that allows students K-5 to learn educational subjects while playing highly engaging computer games.  ABCya is FREE and each activity was created or looked over by certified educators.  Students can find educational games that address letters, numbers, and other important concepts.  ABCya also has a teacher and parent section for more information on how to use this site.  There is a great selection of iPad apps available too.  If you are interested in K-5 education I highly encourage you to check this site out for yourself.