I love old cameras. I have a small collection including a couple of Nikons, Olympus, Pentax and even an old Polaroid camera. Sadly never use them these days. I do use my older Nikon lenses with my DSLR though.
There are some amazing bargains around. You can buy really good SLR bodies for peanuts; I was looking at a Nikon F100 with battery grip and data back for just £130 the other day. That’s something like £1400+ new when it was the latest thing. Interestingly though, the older ‘pro’ bodies seem to retain value. Nikon F2s, F3s, Olympus OM4 Ti, Canon F1s, Pentax LX were THE top SLR bodies, and they aren’t cheap. But something like a Canon A1, an excellent camera, will be very cheap. And Canon FD lenses are cheap because they aren’t compatible with the new EOS systems. Like this beauty:
http://www.ffordes.com/product/15061116090431
Of course, there’s the Pentax K1000, the favourite of photography students. Bomb-proof and reliable. Millions of K-mount lenses available. You could buy a load of macro gear which would once have cost a fortune, for very little money now. Or just a super-sharp SMC 50mm f1.7 for £25.