September 11th candle lighting ceremony., originally uploaded by matt coats.

Gothamist has the details on this annual NYC ritual:

Starting at 6 p.m. (on the south side of Pier 40) lanterns will be prepared, with messages and the names of loved one's. This will be followed by music, meditation and prayer by religious leaders. At 7:45 p.m. the lanterns, lit up, will start floating down the Hudson River, as Sutra Chanting is led by Rev. TK Nakagaki, of the NY Buddhist Church.

The church notes that the "ancient custom of Floating lighted Lanterns in the waterways is a symbolic way of respecting the lives that have gone before us. It can represent a light of hope for peace and harmony."