Chicago--W.W. Grainger, the giant distributor of maintenance, repair and operating supplies, has begun offering online auctions on its Web site, www.grainger.com. Grainger Auction allows customers to bid on surplus MRO products. Currently, Grainger lists $5 million in auction inventory on its site. Forrester Research, Cambridge, Mass., has estimated that the online business-to-business auction market will reach $52.6 billion by 2002. Grainger Auction is powered by FairMarket, a provider of auction technology and services.