I bought the national annual pass again. It's good for 12 months from the month of purchase. It gets you in all of the national parks.
The price went up though, last year it was $50 and now it's $80.
If you are 65 or over, it's $10. Note: It does NOT open the gate at Assateague.
I figure what the heck, it will still save me some bucks because I hit a lot of the national parks. It can be purchased at the link below and if ordered this week, you SHOULD get it in time for the spring fling.
http://store.usgs.gov/pass/