Via the Upgrade Travel Blog, USAirways is selling day passes to its lounges for $25 through August 31 — rather than their usual $40 — by mentioning promo code ES25. Details here.
Most US carriers sell day passes for $50, though $25 is the usual price for access to the Alaska Airlines Boardroom without a membership. (Boardroom members can buy day passes as gifts for only $15, and a year and a half back Alaska was selling these around Christmastime for only $12.50.)