If you come to our house and take a look at the walls, you'll notice something interesting. I collect and frame stamps. Not just any stamps, of course. I'm drawn to U.S. science stamps. My biggest collection is space-themed. I have these 2000 Hubble telescope images accompanied by a poster, this awesome 1997 Mars Pathfinder stamp, and this 1994 Moon Landing 25th Anniversary Sheet, among others.
I'm also fond of a current annual stamp series known as Nature of America, which profiles different U.S. ecosystems. The USPS has issued ten in this series so far, including stamps depicting the Sonoran Desert, the Great Plains Prairie, and the Pacific Coral Reef.
Why collect science stamps? It's a fun and inexpensive hobby that's easy to share with children. Almost any topic or interest can be found on a stamp. For example ...
Like cats? Check out Rhea's Topical Cats Collection.
Dinosaurs? Start with these 1989 dinosaur stamps.
Minerals? Philatelic Mineralogy has images of "Gem, Rock, and Mineral Postage Stamps From Around the World," including pages dedicated to opals, diamonds, and agate (and so much more!).
If you're new to collecting stamps, visit the American Philatelic Society to Learn About Stamps and pick up some Fun Facts.