Santa Clara, Calif.--Joining the ever larger business-to-business electronic commerce bandwagon, Internet portal Yahoo! introduced its Yahoo! B2B Marketplace Monday. On its directory of b-to-b products for sale, Yahoo! aggregates the listings of a handful of independent e-marketplaces, including DoveBid Inc., Freemarkets.com's AssetExhange, Imark.com and Tradeout.com. On its site, Yahoo! B2B Marketplace will provide users access to about 48,000 initial listings in 650 b-to-b categories, according to a press release. The site will integrate with current Yahoo! features such as Yahoo! Calendar, Yahoo! News and Yahoo! Broadcast.