Buy a 30- or 90-day pass: American has a 30-day pass for $99. Delta has one for $90, which includes as many as two guests. US Airways has a 120-day pass for $120.
Get an upscale credit card: Some cards give you lounge access, such as the American Express Platinum Card ($450 a year). Ameriprise World Elite MasterCard ($150 a year) and the Delta SkyMiles Reserve Card ($450 a year). Diners Club International was sold to the Bank of Montreal and is not taking applications for new cards in the U.S.
Join the club: Delta, United, US Airways and American charge an annual fee ranging from $450-$500. That includes unlimited visits to that airline's lounges, plus limited access to SkyTeam or Star Alliance partner airline lounges around the world.