A friend just posted Wonder Woman postage stamps. They have been out since last fall to commemorate her 75th anniversary. I didn’t know that. I got some today! I don’t snail mail many things, so luckily I can just save them and not use them!
I am going to start collecting them. You can get some old issues on Amazon, Ebay and auction sites, but the USPS has some for sale like Batman Forever and Charlie Brown and some others like the Sunday Funnies series which includes Calvin and Hobbes, Beetle Bailey and Dennis the Menace.