http://website.grader.com/ 
Free
Features:
- Provides a unique grade for any given website under its proprietary algorithm.
- The algorithm uses a proprietary blend of over 50 different variables.
- Provides some basic advice on how the website can be improved from a marketing perspective.
- Measures both on-site and off-site parameters to evaluate performance.
- Displays important ranking factors for competitor websites.
How it works:
The algorithm used by web site grader consists of important variables from search engine data, website structure, approximate traffic, site performance and others. The score incorporates things like website traffic, SEO, social popularity and other technical factors which are begin updated continously.