Antique Photography is a great collectable hobby that can be started very cheaply and easily.
All you need to start is a simple old camera such as the famous Box Brownie, you can then add onto this with something like a classic Polaroid camera. There are loads of different types of classic cameras that are superb value for money in todays market. All of the major manufacturers from Leica to Kodak, Minolta have been in business long enough to have a classic film camera around.
You could always move from still photography to a movie camera with a projector. I remember Super 8 film from years ago and it was great fun to watch in the pre-video age.
The older cameras and associated equipment such as reel to reel editors have a wonderful retro look to them so not only are they great to collect but they are good to display.