The list of currently free apps is updated each week. Highlights this week include Purple Frog to teach social skills including caring, DoReMi 1-2-3: Music for kids which focuses on music, Mathzilla for elementary Maths. Cookie Next Door which encourages creativity through Storytelling, and PixStop for Stop Animation. Please visit the web page for additional apps that are currently free.
For more recommendations and reviews of apps for iDevices in the classroom, see http://tips2012.edublogs.org/category/app-recommendations/ and http://teachwithyouripad.wikispaces.com/Blooms+Taxonomy+with+Apps.