Just got this in my inbox. Thought you might appreciate the info!

To continue the city-wide show of support as the Ravens advance in the NFL postseason, the National Aquarium, Baltimore will once again offer a special $5 discount on general admission tickets to guests wearing Ravens or purple apparel on Friday, January 20. The promotion is available through on-site admission ticket purchasing only. The discount will apply only for operating hours of 10 a.m. – 5 p.m. on January 20, 2012. One discount per person. Cannot be combined with any other offers.

Visitors are encouraged to join Aquarium staff in wearing their purple Ravens gear on Purple Friday, January 20 and for the rest of the weekend.