A bible for SEO followers in these difficult days, However it is rooted in old SEO. We would never buy links or reciprocal links. This said there are lots of useful tools for instance:
Similar Page Checker
Search Engine Spider Simulator
Backlink Anchor Text Analysis
Backlink Summary
Keyword Density Cloud
Search Engine Friendly Redirect Check
Google PageRank Tool
Cloaking Checker
Domain Stats Tool
Domain Age Tool
Keyword Playground
Website Keyword Suggestions
URL Rewriting Tool
Keyword-Rich Domain Suggestions
Alexa Rank Checker
301 Redirect
Site Hits: 431 today, 183 yesterday, 2,671 this month, 5,297 last month, 965,039 total System Hits: 41,618 today, 143,481 yesterday, 1,213,396 this month, 3,821,035 last month, 1,598,262,057 total