There have been a few different attempts at sending email via good old snail mail, but this is the first that looks promising to me. Snail Mail My Email sounds like an interesting service, and the big difference from other services is that your email is actually handwritten before being sent off.
I can already see this service being quite useful, especially if some of your family have computer troubles or don’t like using email. They’ll be surprised to get this handwritten note from you.
I can already see many grandmas getting those letters and being quite happy about it. If it could be partially automated, send them an email, and the letter is printed, put in an envelope and posted, that could also be very handy.
The service works off the generosity of volunteers, and the first round of e-mail to snail mail requests have already reached capacity. They plan on accepting more writing volunteers in future, but can still use help to coordinate other groups of volunteers. You can check with them here to see if they still need any more assistance.