Moveable sights and treats in NYC

This thread is dedicated to things in New York that don't have a fixed location, but are always on the move. I'll add to it as I think of new treats.

1. The Renaissance Street Singers
www.streetsingers.org
A group founded in the 70's who give free public concerts of 15th and 16th century acapella motets on the sidewalks of New York. They can be found on Sundays somewhere in the five Boroughs. If you're interested in tracking them down, they usually announce the site of their upcoming concerts on their website.
2. The Van Leeuwen artisan ice cream trucks.
This is not your average ice cream truck experience. The ice cream is just unbelievably tasty, with flavors like Giandujia, Red Currant, and Ginger. They also have classics like Vanilla, Chocolate, and Pistachio, made with natural ingredients that give this ice cream its incredible taste. Spotting one of these yellow trucks is pure happiness, even in wintertime.
Daily truck locations can be found out by following them on Twitter.