Volatility Index (^VIX)

Don't be vexed by a high VIX

Excerpt:

The VIX is officially the Chicago Board Options Exchange Volatility Index, and it measures the market's expectation of future volatility based on Standard and Poor's 500 stock index options prices.
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Turns out the volatility we're experiencing today isn't terribly unusual, even though it might feel that way after the steady run it follows. In the past decade, the VIX traded above 40 three times: During the Russian debt crises in 1998, after 9/11, and during the market downturn of 2002. The VIX's historical average going back to the early 1990s is about 19.

Wiki: VIX

CBOE VOLATILITY INDEX

Comment: Today was the first I've heard of this index! Interesting