Here are my favorite resources:
Glycerin Leaves [Tinkerlab]
How to Preserve Fall Leaves and Branches with Glycerin [Today's Homeowner]
Preserving Leaves [Martha Stewart]
Have you preserved leaves? What method did you use?
The labeled image at the top of the post would also make a good learning tool but it cannot replace the experience of holding an actual leaf. Most of the trees are peaking in Washington Square Park so this is a good time to visit for fall foliage. If you can't make it to the park, enjoy its autumnal show through the photos below.
P.S. The species represented above are different from the ones whose leaves I gathered days after Hurricane Sandy in 2012. The leaf litter I observed in Washington Square Park after the superstorm was heavy on the oaks.