Make Mail Fun Again!
Here's a quick-and-dirty idea: postcards. They're cheap to print or buy, affordable to mail, and fun to receive. Some ideas:
• Invitation to an afternoon of Munchkin, complete with a special rule you put in the postcard.
• A mysterious map for players in a campaign for The Fantasy Trip. Include a cryptic note: "Help me, adventurer!" And see what they do with it. For ideas and inspiration, check out the free download of The Fantasy Trip 2019 Postcard Contest
• An in-game note for a specific player in your GURPS game. Maybe it's a tantalizing tip from a hidden ally, an ominous warning from a mysterious organization, or an idle threat from a mastermind. (Just don't make it too scary, in case the postal carrier gets nervous.)
If anyone uses any of these ideas, is inspired to do something cool and different, or has done something similar in the past, I'd love to hear about it on the forums!
-- Steven Marsh