Saturday September 29th is National Public Lands Day

-- National Public Lands Day website

-- The National Park Service, U.S. Fish and Wildlife Service, U.S. Forest Service and the Bureau of Land Management have all declared National Public Lands Day on September 29, 2012 as a fee-free day. The Army Corps of Engineers has waived day-use fees at their parks.
-- list of fee-free days for national public lands

From the webpage:

More than 170,000 volunteers are expected at more than 2,100 sites across the country on Saturday, September 29 to take part in the largest single-day volunteer effort for public lands in the United States, National Public Lands Day (NPLD).

Volunteers in every state will visit parks, public and community gardens, beaches, wildlife preserves or forests and chip in to help these treasured places that belong to all Americans. They will improve and restore the lands and facilities the public uses for recreation, education, exercise and connecting with nature. ...

 

Events in every state, the District of Columbia and many U.S. territories can be found online now, searchable by state or zip code. Eight federal agencies will participate—along with more than 250 state, county and city partners, and a host of nonprofit organizations around the nation.
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Not part of National Public Lands Day, there will be a cleanup of the Triangle Park in Takoma, at 4th Street and Blair Road NW on Saturday, from 10am to 12 noon.

The park is somewhat contentious because it is used most heavily by a group of public drinkers, most aren't homeless, who don't make the park very hospitable for use by others. 

I argue that part of the problem is that the park is designed to shield users from "eyes in the street," cloaking negative behaviors.  Others make the point that it's in such a bad location, at the triangular corner of a traffic sewer, that it's not really very conducive to being used anyway.