I really liked some of the courses on Highbrow. A bit hit or miss, but it allows you to get slightly stuck into a single subject over a week or so
EDIT: Just saw where you work.... well its a compliment i guess then at least?
Owl is a simple app that sends you a new fact to learn each day. If you're not looking to learn something specific, like a language or skill, this is a simple app that will boost you're overall general knowledge.