Site/Domain Attributes
The factors below contribute to Google's rankings based on the site/domain on which a page resides.
Global Link Popularity of Site
The overall link weight/authority as measured by links from any and all sites across the web (both link quality and quantity)
4.4    Exceptional Importance
Age of Site
Not the date of original registration of the domain, but rather the launch of indexable content seen by the search engines (note that this can change if a domain switches ownership)
4.1    Exceptional Importance
Topical Relevance of Inbound Links to Site
The subject-specific relationship between the sites/pages linking to the target page and the target keyword
3.9    High Importance
Link Popularity of Site in Topical Community
The link weight/authority of the target website amongst its topical peers in the online world
3.9     High Importance
Rate of New Inbound Links to Site
The frequency and timing of external sites linking in to the given domain
3.5     High Importance
Relevance of Site's Primary Subject Matter to Query
The topical relationships between the full content of a website and a user's given query
3.1    High Importance
Historical Performance of Site as Measured by Time Spent on Page, Clickthroughs from SERPs, Direct Visits, Bookmarks, etc.
Metric of click-through-rate, time spent on a page/site, direct navigation via bookmarks, etc. that Google may be measuring through use of their toolbar, free wifi, Google analytics, etc. (note that this is purely speculation as Google has never publicly admitted to monitoring or recording this data)
2.8     Moderate Importance

Manual Authority/Weight Given to Site by Google
Google is occassionally suspected or accused of applying manual manipulation to a domain or page (note that this factor refers specifically to positive ranking manipulation)
2.6     Moderate Importance
TLD Extension of Site (edu, gov, us, ca, com, etc)
The top-level domain extension of the site. Note that some domains, such as .edu, .gov, .mil and others have restrictions on who may purchase them
2.6     Moderate Importance
Rate of New Pages Added to Site
The amount & frequency of new, spiderable documents added to the domain over time
2.5      Moderate Importance
Number of Queries for Site/Domain over Time
The frequency of searches for the domain name or the company/organization's brand as measured through Google's search query logs
2      Moderate Importance
Verification of Site with Google Webmaster Central
1.3     Slight Importance