The affected pills are Lo/Ovral-28 and generic Norgestrel and Ethinyl Estradiol tablets. The packets have expiration dates ranging between July 31, 2013 and March 31, 2014, and lot numbers are available at at this site.
For those of you not familiar with the alchemy involved with hormal contraceptives, birth control packets contain three weeks of "active" pills — or those containing hormones — followed by sugar pills. In the Pfizer mix-up, many of the affected packets had too many or too few of the active pills.
Anyone with affected pills should return them to the pharmacy, and maybe pick up a pregnancy test while you're there.