Etsy seller Recycled Ideas makes greeting cards with embedded seeds; once you've read and appreciated the message, you can plant the card and watch it sprout.
Love the earth? Me too! My passion for primates led me to study them and in doing so, I learned of their precarious position on earth. So many are endangered because their habitat is being destroyed everyday. That's why I make green gifts – like plantable paper.
See also: Business card that sprouts