NYC Parks & Recreation sponsors MulchFest 2010 — instead of throwing your tree in the trash, drag it over to Corlears Hook Park on Saturday and Sunday, January 9 and 10, between 10am and 2pm. They’ll be collecting trees to chip down for mulch throughout the city’s parks.
Update: Apparently NYC Sanitation Dep’t is collecting trees this year for mulch as well, from Jan. 4 through Jan. 15. Just leave the tree out on the curb for regular pickup, with no ornaments, stands, or bags. (There had been talk in the fall of suspending this program for budgetary reasons, but apparently it’s been restored.)