Many of the nature in art sites I've found are filled with activities for parents to do with their kids, or teachers with their students. But I don't see anything wrong with adults trying out some of these projects, or looking at the resources.
Martha Stewart's Back to Kids' Nature Craft is a great place to visit and find many artistic projects with nature as a theme, like this fabric bracelet (left). Whether you enjoy hunting for seashells or going on nature walks, you'll find something fun to do on the weekend or holiday with Martha!
Here's an easy way to make an attractive window box herb garden for your kitchen. There's not a lot of expensive supplies, and you may have some of the items needed around the house already. I think adding your own personality to this little wooden box would be fun. A great idea for the cook in the family.
If you're a serious artist and are interested in promoting nature art and conservation, you might want to stop by the Artists for Conservation (AFC) homepage. They're an international non-profit group of nature artists. There's a steep annual membership, but the benefits outweigh the costs if you're an active member. Their Annual Exhibition this year is at Grouse Mountain, Vancouver from October 12 through the 21st. Check it out.
Earth, Sea, Sun, and Sky by Barbara Stieff. It's especially geared towards the young reader. Anyone can take these ideas and transform them into their own. If you have children and are looking for creative projects, this book looks to be a good guide.
listing of 129 different teams. The smallest ones have only one member; the largest, over 900. If you're an Etsy member and you enjoy nature, join a nature team and meet some like-minded people. I picked out nine that looked really neat!