Eliminate the tax exemption enjoyed by the U.S. Chamber of Commerce as a "trade association." Their independent-expenditure political campaigns pick the pockets of all taxpayers.
Why is this important?
According to the L.A. Times of 5/26/11, the U.S. Chamber of Commerce spent $33 million last year on advertising to influence political races without disclosing its donors. Why should they have tax-exempt status? (They also have reportedly raised more than $80 million to spend for the same purpose in the 2012 election cycle.)