A term commonly used in futures markets. Contango occurs when the spot price of a commodity is lower than the price of a contract for future delivery, or more generally, when far futures are more expensive than near futures. In other words, people are willing to pay to not have to take immediate possession of something that they wish to have at some future time. Contango is the opposite of backwardation.
Earlier this year, there was an extreme case of contango in the crude oil market, as 6 month contracts were trading at around $15 per barrel above spot. Apparently the greedy buggers in OPEC pumped lots more of the stuff than demand warranted, which overwhelmed the available storage capacity. Trading firms leased huge tanker ships, effectively using them as floating storage tanks.