Mark your calendar for these fee-free days in 2011:

• January 15-17
  (Martin Luther King, Jr. Birthday weekend)
• April 16-24
  (National Park Week)
• June 21
  (First day of summer)
• September 24
  (Public Lands Day)
• November 11-13
  (Veterans Day weekend)

Making the fun even more affordable, many national park concessioners are joining the National Park Service in welcoming visitors with their own special offers.

http://www.nps.gov/findapark/feefreeparks.htm