http://services.google.com/websiteoptimizer/
Google Website Optimizer is a promising multivariate testing tool to optimize landing pages. At the time of this post, it is being beta tested.
This looks like it will be an awesome tool for the solo direct marketers, as this kind of software currently costs major buckage.
Here's a review:
http://www.chris-hooley.com/2006/11/...ting-platform/