They say collecting post stamps is an interesting and educational hobby... I think they're right.
Some people even like motorcycles and post stamps.
Here is a collection of international post stamps on one theme: TRIAL
More trial post stamps can be found here: http://www.mfnl.nl/Nieuwsbrief/NB84/NB84Trial.html
(Text in Dutch)
7 Hungarian vintage post stamps (1962) private collection.