The Denver Post has posted a nice little article about the barter boom in Colorado, which is consistent with previous articles I've noticed about trends in other states and countries. The main online venue seems to be none other than Craigslist, which provides a way for buyers and sellers to connect and then negotiate their terms (which might not involve the exchange of money buy of goods and services -- Craigslist even has a barter category to grease the wheels). Naturally, the IRS says that barter transactions are income and therefore taxable (along with garage sales and probably the lemonade stand run by your neighbor's kid), but I have my doubts that anyone can trace the huge number of barter transactions that are happening.