Creddon - Tweet for a cause and a sponsor will donate $1 to charity
Cringemail - Poke fun at your friends by sending them a postcard
Send Mail Get Mail - A postcard-sending website.
Inkpact - Send genuine handwritten messages in just a few clicks
Postacard - Text a photo to send it as a postcard for $3.
Letterly - Send handwritten cards to family and friends