UPDATE:
JavaScript Blacklist Safari Extension 1.0.1 is available.
What is Drew Thaler’s JavaScript Blacklist Safari Extension?
JavaScript Blacklist is a simple extension for Safari 5 which blacklists scripts from a configurable list of domains. If a common “utility” script used by sites that you visit is annoying you, this will let you opt out quickly and easily.
John Gruber linked to Drew Thaler’s page which was hosted on MobileMe: http://homepage.mac.com/drewthaler/jsblacklist/
The problem is that Apple has shut MobileMe down starting July 1st, 2012.
You can easily copy Drew Thaler’s JavaScript Blacklist Safari Extension from other computers. You can also download it here. I copied it from one of my computers and zipped it.