Via Watershed Studio:

Expired: Now through June 30th, 2009 you can purchase OIOpublisher for just $37 (normally $47) by using coupon code “MIDSUM-WSHED” (no quotes).

[Update: August 2010 OIOpublisher Coupon Code - Now through August 31st, 2010 you can purchase OIOpublisher* for just $37 (normally $47) by using coupon code "SOLAR-WSHED" (no quotes).]