Just an idea for now, but if anyone wants to use them feel free to. Though there might be changes coming down the pike.
Updated 2/21/13 to reflect the latest changes.As we're always trying to ramp up our efforts to get all the cool trucks and people into our club here I thought we might consider leaving calling cards on vehicles we spot. I came up with a bit of a template that looks like this:

And now in color:

I've added this to an Avery template that's compatible with nearly any version of Word and Open Office and can be printed over on Avery Business Card templates including:
Compatible Avery Products:
15871, 18871, 27871, 27881, 27882, 27883, 28371, 28865, 28873, 28876, 28877, 28878, 38871, 38873, 38876, 5371, 5376, 5377, 55871, 55876, 5870, 5871, 5872, 5873, 5874, 5876, 5877, 5878, 5882, 5911, 8271, 8371, 8372, 8376, 8377, 8471, 8476, 8571, 8865, 8870, 8871, 8872, 8873, 8874, 8875, 8876, 8877, 8878, 8879
And of course other off brand brand products that are compatible with Avery's 3.5"x2" cards lined in 5x2 per sheet should also work.
Here are the printable templates:
Black and white:
DownloadColor:
DownloadIf that doesn't download permanently, you should be able to do a right click > Save Target As... download.
Also each spot has text labeled {Type Your Name Here} - If you do a find/replace in Word with your user name then it will automatically generate a sheet of ten cards personalized for you.
Hope that helps our spotting/recruiting efforts