This movie of a ball rolling across the surface of a rotating merry-go-round is a helpful demonstration of the Coriolis force (Courtesy: Univ. of Illinois, Dept. of Atmospheric Sciences).
Further Reading:
Two articles on the nature of the Coriolis force can be found here:
Phillips, Norman A. 2000: An Explication of the Coriolis Effect. Bulletin of the American Meteorological Society: Vol. 81, No. 2, pp. 299-304. pdf
Persson, Anders. 1998: How Do We Understand the Coriolis Force?. Bulletin of the American Meteorological Society: Vol. 79, No. 7, pp. 1373-1385. pdf