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
|Devil Rock (Stuttgart, Germany) by cornissimo|
from Neon Signs
|Carla... by lickity split|
from Beautiful caucasian female faces
|Lunar New Year Fireworks by Michael L NYC 99|
|Vatican Basilica by wam7|
from Street lights