Although I have saved most of that stuff in plastic bags, my best trip "souvenirs" are the weekend updates, (or trip updates) my husband started writing to our families when we moved to England over three years ago. They have all been saved in an album and will be fun to look at once we have repatriated. I imagine our stuff (passages, etc) will be put in the circular file at some point, but the album will always be kept.
Cheers, Pam