ITEX

Monthly fee: $20, plus 10 barter dollars
Commission: 7.5 percent of each transaction from both buyer and seller; 6 percent if you provide a credit card in advance
Members: 24,000

International Monetary Systems

Monthly fee: $15, plus 15 barter dollars. The fee is waived for the first six months.
Commission: 7.5 percent of each transaction from both buyer and seller
Members: About 17,500

Barter Bucks Banc

Monthly fee: $12
Commission: 5 percent from both buyer and seller
Members: 52,000 through DoBarter, a network of independent barter exchanges