"Finding apps isn’t difficult. Finding education apps is only a bit more challenging. Finding free education apps is also possible. Finding free education apps worth downloading is a different story entirely.
The following is our list for the 55 best apps for learning we can find. Some are formal learning–math drilling and phonics, for example–while others are RSS readers, social media platforms, and the like. Nonetheless, these represent the 55 best we could find as of Q1 2013."
Via John Evans, Fabrice Vezin