Science's 10 most beautiful experiments [via]. Enjoyable, although I'd put experiments like electron diffraction down as illustration instead.

My personal favourite, not on the list, is the Michelson-Morley experiment (see also this simulation in Flash). It showed that light isn't, like sound, a wave travelling in some other medium. Until this experiment, in 1887, such a universal medium, called the aether, was suspected. The equipment is simple: A empty box and some mirrors. By looking inward and closely at a careful arrangement in your lab, a property of the whole physical universe is revealed. Michelson-Morley was one of the first lab experiments I did at college.