This is an easy project we did the last time we went to the river. I call them "Wilding Sticks". All you need is a variety of colorful electrical tape, scissors, and some feathers. After you've collected the walking sticks, add the tape and feathers in whatever design is appealing. I think they're so cool to look at and the kids love using them.
We also made these nature bracelets which were very easy. Make a bracelet of duct tape with the sticky side out. Now, collect bits and pieces of flowers, seeds, grasses and other things you find and stick them on the bracelet. I like this project because it really tunes you into the variety of plant-life growing around you.