Here's a zippy little article on the evolution of integration that I found while preparing for tomorrow's multivariable calculus lecture. (I'll be showing the young 'uns the triple integral, and was wondering if I could make the idea of Jordan measure comprehensible at this level.) The bit at the end is the interesting part--I hadn't realised that the existence or nonexistence of certain measures could have set-theoretical consequences. Like inaccessible cardinals. Who knew?