Today BBC radio carried a story about the rampant hyperinflation in Zimbabwe. One man who was interviewed said his daily expenses were about 600 BILLION dollars, including 100 billion for a loaf of bread.
The official inflation rate is 2 million percent per year, but most observers feel that is an underestimate. This is reminiscent of the hyperinflation that hit Hungary in 1945-46; here's a chart of the number of billion pengos per one gold franc -
That's for just a ten-day period.
Yugoslavia experienced hyperinflation in 1993; from October 1993 to January 1995 prices increased 5 QUADRILLION percent (5,000,000,000,000,000%).
In the next couple years the inflation rate in the U.S. will heat up; when it reaches 10-12%, people will talk about "hyperinflation," but that's nothing compared to historic hyperinflations. Wiki has a compilation of these episodes.
Update 01/16/09: Zimbabwe has introduced a Z$100 trillion note.