iPath S&P 500 VIX Short-Term Futures ETN (NYSEARCA:VXX) a popular measure of the implied volatility of S&P 500 index Options
The iPath S&P 500 VIX Short-Term Futures ETN (NYSEARCA:VXX) prices itself off of the average and implied volatility of the first two months of futures contracts of the S&P 500 Index
VelocityShares Daily 2X VIX Short-Term ETN (NYSEARCA:TVIX) This ETN is designed to track 2X return on volatility in the markets as measured by the VIX Short-Term Futures Index.
iPath S&P 500 VIX Mid-Term Futures ETN (NYSEARCA:VXZ) is priced from the average volatility of the 4th through 7th month futures contracts
S&P 500 Dynamic VIX ETN (NYSEARCA:XVZ) Short-Term Futures Index Excess Return and the S&P 500 VIX Mid-Term Futures
Velocity Shares Daily Inverse VIX Short-Term ETN (NYSEARCA:XIV) inversely track the volatility in the markets as measured by the S&P 500 VIX Short-Term Futures Index