I am looking for automated website testing software.  It is to test a
shopping cart checkout system, among other things.  The cost of the
software is not important.

Hello russelz:

Thanks for the interesting question. 

The most complete listing of automated web testing software/services
that I was able to find is at:

ATS - Web and E-Commerce Testing
URL: http://www.sqa-test.com/webtest.html

I've looked through these sites, and given your criteria above, I'd
recommend starting your search with:

QACenter Enterprise Edition
Company: Compuware 
URL: http://www.compuware.com/products/qacenter/enterprise.htm

WinRunner
Company: Mercury
URL: http://www.mercury.com/us/products/quality-center/functional-testing/winrunner/

If, once you look into these two products, you'd like to narrow down
exactly what you're looking for, I'd be more than happy to do some
more investigation for you.

Search Strategy (on Google):
* "automated web testing"
* "automated website testing"
* "automated e-commerce testing"
* Rational SiteMorse

Please let me know if you require clarification of this answer. Thanks. 

websearcher

generally webtesting should need load runner software..
it makes all kind of webbased functionaly..
like load test..etc.
just u can refer the mercury site.....it is free for 14 days trial..