Pen pal letters...post it note doodles...mini folded zines...tiny abstract paintings...fun stickers...etc.! I've even printed out silly internet memes and made paper collages with them. Postal correspondence is a great way to brighten someone's day...and opening your mailbox to find an envelope hand-addressed to you with Good Stuff inside from someone you care about? It sure beats just getting bills and junk mail!
Simple way to show you're thinking of your people. Sure, challenges include sourcing peoples' addresses and then finding a place that sells stamps. But surprising your friends and fam with a postcard in the mail is worth the extra hassle.