I have younger kids and they only get on once or twice a week ( unless we are all sick and just zoning out at home) , but here are some faves:

Park Math - basic counting, addition and subtraction concepts. 3-4.
Word Wagon - find letters, make words. Letter recognition. 3+
Tangrams - Shape puzzles. My 3 year old is obsessed with this. He is a puzzle fiend though.
SuperWhy - letters, rhyming, etc. eh.
Bus - this was our first app. Wheels on the bus. 2+. Cute.
Lunch Box - I don't even know what this is about but the boy loves it. All I hear are a annoying monkey sounds. He gets stickers.

Books that are good:
Land of me. Tell a story in different ways. Really neat.
Fox in socks. Anything that will spare me reading this tongue twister gets my votes.
Toy story. 3 yr old obsessed with Woody.
Finding Nemo / various Mickey books. Many of these have puzzles. He seems to find new and interesting things every time he reads them.
Monster at the end of the book. Hysterical.

pachouly