On January 1, 2009, the qualified bicycle commuting reimbursement was added to the list of qualified transportation fringe benefits covered in section 132 (f) of the Internal Revenue Service Code.  Chances are, you haven’t heard about this much or how you can take advantage.
The League of American Bicyclists has a continually updated web page to help you and your employer get set up to offer the $20/month bicycle commuter credit.
They have tons of links and information…check it out here.