The event is major, as there are almost 2,000 improvement projects slated for courty, state and federal parks, wildlife refuges and national forests.

In Yellowstone, volunteers will be working on trail restoration along the Clear Lake—Ribbon Lake Loop Trail, located in the Canyon area. They'll be installing water bars that will greatly improve the conditions on the trail. Enough volunteers have already signed up for the Yellowstone restoration work, but that shouldn't stop you from a free visit anyway.

It's also a good weekend for one last hurrah. Many services in Yellowstone close at the end of business Sunday: the Old Faithful Lodge complex and the Tower Fall Store, for example. You can see a full list of 2011 opening and closing dates here.

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