B&H has the Bolt Cyclone DR PP-400DR Dual Outlet Power Pack for $249.95 (reg. $499.95) through today (March 6) only. the power pack works with Canon, Nikon, Sony and other speedlights with high-voltage connections and offers up to 1400 full-power flashes. Check it out here at B&H Photo.
There are other Bolt power pack units on sale as well. Check them out here at B&H Photo.