For the vendor at the University of Rochester last Christmas I made a bunch of sorority stamps of the greek letters. I still have some left, and I have posted them in my Etsy shop. These are easy to carve, and I can carve any sorority or fraternity's letters, in any size as a custom item as well.
I think these look great on a letter, envelope, card, t-shirt, or any other craft item you can stamp on! The sky is really the limit on uses.
Each stamp is individual, and comes in a set. I made each greek letter separate so the stamper can decide if they want a horizontal, vertical, diagonal, or random pattern when stamping.