Does anyone else collect public transport tickets? How should I display my collection?

I’ve just got back from a trip and managed to collect a rapid/mass transit ticket from almost every city we visited (damn you Cleveland) – a combination of metro, light rail and bus networks predominantly.

How should I display them? I don’t want to glue them into a book because both sides of the ticket are interesting, but considering the different form factors and sizes, a basic display folder won’t be very secure.