Although we're in a digital age, our students still work on handwriting letters and learning the parts to a friendly letter. We also work on addressing envelopes and writing information in the appropriate spots!
I've been doing this project for about 4 years now and it's a hit every single time! I've only had a few students unable to participate sending letters out (they have written to me and our principal instead) and I've only had a few students unable to bring in stamps (I've always had a parent every year send in extra!).
Here's how it works, I introduce the topic of writing letters with the students and we teach the format through several practice writings (we pretend write to authors we love, each other, and so on). I then hand out this permission slip asking parents who are willing to let their children participate send in stamps and addresses. I keep things separated in Ziplocs or envelopes for each student.
We begin to write our letters in pencil, edit, etc. and after we've sent out several and begin to receive letters back, this becomes a station in my guided reading groups using the app Evernote! It's AWESOME and the kids truly enjoy it. I'm able to edit their notes and the students can edit each other's. We teach explicit ways to edit and respect each other's work.
Let me know if you need any other information - this is just a file to get you started! I've had students in the past who have written to relatives all over the USA and overseas and we kept track on a map! They couldn't wait to get "snail mail". (They really began to understand that letters take longer to come than an instant email... patience!!)