Cheaper Sheet Plastic For Model Building‏

[ChalkLine]

It's not polystyrene but ABS and PET plastic sheet is easily available in 0.5mm and 1.0mm in fairly large sheets for just a few bucks online. The PET is supposedly for picture frames and actually varies between 0.7mm to just over 1.0mm.

[Kerick]

That would be better than the garage sale signs were you have to sand the ink of to get it to take glue.

[apophenia]

That would be better than the garage sale signs were you have to sand the ink of to get it to take glue.

That takes me back ... 

[ChalkLine]

Not plastic but sheet copper, I picked up a pack sort of like these (a little bit bigger in size) for $5 to use as copper foil at a hardware store gardening centre

[Kerick]

Interesting! And I was just looking up brass shim stock online last night. Lots of options there.

[Frank3k]

You can also get a "lifetime" supply of that copper foil in rolls  - look for snail barriers. The adhesive on the backside can be both helpful and a hindrance. The copper is also conductive (no protective coat) so it's great if you need to run power to an LED or other component but don't have the space to run wires.