Email is great. You need to set a date, ask a question, opine on some esoteric subject--and your friends grab their agendas, answer, agree, or disagree.
Communication happens fast and at your schedule. (Big plus for myself who doesn't like to be interrupted.) If you want to share some detail immediately and it's 5 a.m. where your friend lives, go ahead, type an email. Your friend will read it at her convenience and you can read her reply at your convenience.
Snail mail isn't as fast or hot off the tongue, but it can be more quirky, personal, and fun. Yesterday I got a letter from a friend on this lovely stationary decorated with bits of curved ribbon.
I've received snail mail on handmade, organic, coloured, scratchy, and velvety paper. Postcards and cards count too. They don't have to be artsy. Kitsch has its own aesthetic. Pages come adorned with drawings, pasted wine labels, bits of tissue paper collage, coffee circles.
R and I used to live in cities several hours apart. We wrote letters. Now we share a house.
Here's a letter from my friend in Copenhagen: a poem 106 lines / 56 cm / 22" long. I've kept it in the scroll shape it was sent. It's called "Through the Looking Glasses, Markly" because his name is Mark and mine is...