I LOVE props, I spend way too much time looking on eBay and
Prop Store of London
I love making replicas, but being good with computers rather than building things most of my props end up being print replicas.
For example:
Futurama

This was a fridge magnet I made for my desk at work, my blue bottle of water was next to it. Yes, super geeky and obscure!
For those that don't remember the reference:
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[ATTACH]870[/ATTACH]
I also have a replica can of Slurm that I purchased online
Stargate SG-1
This is a collection of printed props from Stargate SG-1, the originals are all high resolution (300dpi) and entirely hand recreated from DVD screenshots, like this one:
Ghostbusters 2
The only thing I have is an ECTO-1A license plate I purchased on eBay from Travis Bell:
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I also bought a BDR529 plate with the registration sticker included.
Back to the Future
I REALLY want to get an "OUTTATIME" license plate one day. And maybe also one of those barcode plates from the 2nd movie. And that replica Flux Capacitor is pretty nifty too, but expensive (as most Master Replicas products are).
For now I have downloaded some print replicas and given them to some friends at work, including the Greys Sports Almanac cover, Doc Brown's business card, the photo of Doc and Marty in Hill Valley with the clock in 1885, the Save the Clock Tower flyer and the Western Union letter left for Marty by Doc in 1885.