I've been using barcode scanners in my chemistry lab for several years.
They have been immensely useful.
I've mainly used the scanner SparkFun sells but I have since found a less expensive scanner on eBay that will work as a serial device (single data pin).
I've posted details of how to make a cable to use the scanner in serial mode in the product page's comments and in SparkFun's forum.
Since my post in SparkFun's forum isn't likely to be seen by the majority of you, I thought I'd post a link here in case it could help a fellow forum member.
I've used the scanners with a Propeller, but they should also work with a Basic Stamp.
Edit: The eBay scanner I have is no longer listed. This one looks like it should work the same way.