Pizza Fractions, Price: FREE, A great way to introduce kids to fractions! It shows a pizza sliced in x amount of slices and from three fractions show you are to pick the correct one.
Skill Builders Spelling, Price: FREE, Create your own spelling lists
Stack the Countries, Price: $1.99, Of course the "Lite" version is free but those only last so long. This would make for a great supplement to any geography curriculum.
Toddler Teasers Shapes, Price: FREE, Shape recognition, I can honestly give this app 90% of the credit for Autumn learning her shapes!
Kindergarten.com Zoo Animals, Price: FREE, there are lots of other flashcard apps like this from kindergarten.com. I gravitated toward this because of the icon. ;) These show real photos and say the name of each animal.