Well known SEO Analyst has reported the top 10 ranked factors across the 5 categories as:

Title Tag - 4.57
Anchor Text of Links - 4.46
Keyword Use in Document Text - 4.38
Accessibility of Document - 4.3
Links to Document from Site-Internal Pages - 4.15
Primary Subject Matter of Site - 4.00
External Links to Linking Pages - 3.92
Link Popularity of Site in Topical Community - 3.77
Global Link Popularity of Site - 3.69
Keyword Spamming - 3.69

Even though this is basically a survey, and results show the participants’ views, this is a great resource to go through before starting to optimize your sites.