We haven't taken a lot of family vacations, so when we do, I like to take lots of pictures and document the event. My new favorite vacation souvenir is the 8x8 photo books from Shutterfly.
A couple of weeks ago, there was a special of buy one, get one 50% off or something like that. I was able to put together a photo book from our family vacation this summer in the Twin Cities
and also from our family vacation last summer to Chicago. In the back of the book, I like to glue in a little envelop to hold various ticket stubs and ephemera from the trip.
I also try to include specifics about what we did and what we liked about the vacation or interesting little things that happened.
Eventually, I would like to have a complete collection of 8x8 books from our family trips. I have a few more to get done, but really for the money, I think this is the best vacation souvenir ever!