If there any national parks you want to visit, these are the days to go (or avoid, depending on your point of view.)
http://www.nps.gov/findapark/feefreeparks.htm
- Jan 15-17: MLK Jr Birthday weekend
- April 16-24
- June 21: first day of summer
- Sept 24th
- Nov 11-13: Verterans’ Day weekend