Any more details about how/where to do this? My grandmother recently passed, and as we were going through her things we found a large amount of V-mail that my grandfather sent to her during WWII. I'd love to preserve it, although I don't know if I'm ready to send the physical items anywhere yet.

For digital artifacts, https://archive.org/create/ (you’ll need to create an archive.org account) is where items can be created.

If you only have physical artifacts, I recommend scanning at 600 dpi for digital artifact creation prior to uploading to the Internet Archive.