Pope Benedict XVI has granted a full plenary Indulgence in honor of our Blessed Mother's Solemnity of the Immaculate Conception on December 8. That's this Thursday.
Here are the basics of what you need to do, the conditions and benefits thereof, etc, and here is a pithy Q&A explanation on what an Indulgence is and is not, by Jimmy Akin.
Indulgences are one of those deliciously Catholic distinctives you don't want to bring up in the first conversation with a Protestant inquiring about the Faith. But a rich and grace-filled reality nonetheless.