With fall just around the corner I can't help but think off all the fun things to do with leaves. I always get a kick out of making leaf prints and then using them for cards -- this is also a neat activity to do with kids. All you need are leaves that have fallen from the trees, some acrylic paint (washable paint if you're working with the kids), and paper.
Once you've found a leaf that you want to use to make your print, just paint the front of it and then press it down on your paper. The amount of paint that you use will determine how detailed your print will be -- play around with it until you find the look that you want. When I did this one I decided to use green and yellow paint on my leaf, and then I did a watercolor wash over it when it was dry.