Axiom is a fun math based iOS app that is free for today. This educational game has players control a ship by tilting their ipad to collect numbers and math signs to solve a equation, similar to the Marble Math games. The game has over 80 levels and gets significantly harder as the levels progress.
Words w/ William is an excellent iOS app for PreK/Toddlers learning the alphabet, numbers, and colors. The way this works is a child watches William and selects the letter, number, or color he asks for. It's very easy to use and has a feature for parents to turn on/off what they want their child to learn.
Easy Studio is an excellent iPad app for teaching kids how to create custom animations. This is done in a very user friendly way that has students use shapes to follow patterns and take screen shots to create animations. The process is not that different then those familiar w/ stop motion. Also, this is done by building on lessons getting more complex as they go along.
StoryToolz is a wonderful site for LA/Writing teachers that I just found out about from Free Technology 4 Teachers. This is fantastic place to find word prompts or story starters for students looking to create a composition. This can be done by choosing either: random conflicts, story idea generator, or half title generator. These buttons create a list of different ideas to create a story. If a person wants to create a new list all they can create a new list w/ a click of a button. 
Discover Indian Monuments w/ Tamarind Tots is a very beautiful looking iPad app that is ideal for teaching kids/students about the different monuments in India such as the Taj Mahal and more. This app not only is very informative as it describes the different landmarks in great interactive detail, it allows youngsters to engage in activities such as connect the dots or swipe the screen to reveal a picture.
Super Teacher Worksheets is one of the best sites around finding worksheets on any number of subjects. Not only can a teacher find printables on different subjects such as: Math, Grammar, Writing, Reading, Spelling, Science, and more a educator can even customize their worksheets for their students. For example, if a Math teacher wants to create their own equations to use for their class this is the place to go. Also, STW is a great place to find and customize different exercises such as word searches, cross words and more.