If you've been stuck at home with kids all year, you've probably already had to get pretty creative to keep them entertained. Luckily there are some great books to help you come up with more activities. Backyard Adventure by Amanda Thomsen has more than fifty activities for playing outside, whether you're working with a yard, the woods, or a patch of sidewalk.
And for even more activities, especially if you live in a more rural area, there's Ben Hewitt's The Young Adventurer's Guide to (Almost) Everything -- fair warning, along with other wilderness survival skills this one does specifically teach kids how to eat bugs and poop in the woods, so be ready for that!