Here is the 2011-12 kindergarten list - some of the basic apps on my student iPads and couple of words on why (a great place to get started):
iStopMotion - even 5 year olds can create really cool "stories" - read more here
iPhoto - so we can edit our photos and create quick journals of field trips, activities, projects

iWriteWords - good for handwriting practice - read more here

Word Wizard - for building words, has many wonderful lists of words already built in (Dolch Sight words, numbers, animals, foods, CVC lists based on specific blends, letter sounds, etc) and lets you enter your own lists - read more here

Montessori Crosswords - fun reading/spelling practice - allows the selection of targeted sounds such as short vowel sound words, specific consonant sounds, digraphs, silent letters - read more here

Book Creator - to give the students the tool to be completely creative in telling a story - read more here

LetterSchool - fantastic handwriting practice - read more here

Motion Math Zoom - interactive number line - great for thinking about number relationships - bigger, smaller, number order - read more here
Motion Math Hungry Fish - fishy way of approaching number relationships/addition - read more here
Moofy Patterns - for practicing patterns

Motion Math Wings - new way to consider "which is more" using a little kinesthetic learning

Scribble Press - for letting the creativity flow (don't miss the outstanding marker wall!)

Big Seed - wonderful problem solving app which gets kids working together, having thinking conversations - read more here
KickBox - a great app for practicing persistence, problem solving, collaborative pairing - read more here

Strip Design - think wordless books in a storyboard format for 6 year olds - a great app for getting the creative juices flowing

StarWalk - because there are wonderful stories in the stars...and a little fun too! read more here

Bumpling - more problem solving, logical thinking, and possibilities for collaborative efforts - read more here