Photo bus cards
Have you seen the "hockey rink" writable CDs?
They fit into a regular 2" x 3.5" North American business card format.
You can put e.g. a small website on them, as well as normal printing on one side.
A bit more expense, and work to create, but can be good attention-getters & info-deliverers.
"hockey rink" cds
|IMG_8168ABCD by citori525|
|McKinley meadow by TimR32225|
from Natural meadows
|Flare-well to a Classic Flying Machine by cjf2|
from Flying Machines
|_DSC2146 by jerste|
from Helios-44 II
|Leopoldsteinersee by RaCor|
from Landscape - Colour #3