Business Value Calculator - Plug in data to determine the Business Value of a Purchase.
Payment Plan Calculator - This calculator will help you determine if you should offer or accept a payment plan or if you should push for a lump sum payment.
SEMRush - Data for SEO/SEM Professionals, keywords, rankings, competition, traffic estimations.
SEOMoz - Very comprehensive SEO analytics. On-page SEO analysis, link analysis, and much more.
OpenSite Explorer - Comprehensive index of link intelligence. Research a site's inbound links.
WhoRush - Map of web assets. Discover relationships between web properties.