One resource I return to always is the Triptico app run by David Riley (a Yorkshireman like myself!). Far from the specific, time-heavy lower-level content education apps that require contexts so specific they are rarely reused, Triptico is perhaps the most user-friendly series of education apps I have used so far.
Most heavily used in my classroom are the selector and word magnet apps. The ability to quickly create groupings for tasks, or to demonstrate sentence adjustment, means that – by my judgement – I can employ these apps with speed and ease.
Right now, David is redesigning the apps with feedback from working teachers and in partnership with NATE: I expect big things from this, especially with it being made by teachers, for teachers.