Domain name age - check domain name availability, domain age, whois.
Keyword Research and Suggestion Tools
SEO Book Keyword Density Tool - tool shows top keyword phrases your webpage is ranking for.
SEOmoz Term Extractor - tool analyses a page and extracts terms that appear to be targeted to search engines.
Google AdWords Keyword Suggestion Tool - free tool to find out related serach terms and keyword competitiveness.
Wordtracker Free Keywords - free keyword suggestions from Wordtracker.
Wordtracker also has a more advanced paid version, and sells top keyword reports.
Google Suggest Tool - shows frequently search for phrases starting with the words and letters in your query.
WordStream Keyword Tool - allows you to export a list of thousands of keywords for free.
Microsoft Keyword Forecast - shows predicted Microsoft search impression count and historical trends.
Wordze - nice for generating decently large keyword lists quickly and inserting them into paid search campaigns.
Yahoo! Search Marketing - has a keyword research tool inside their platform Yahoo keyword tool.
Keyword Valuation Tools
Google Traffic Estimator - shows the estimated bids prices and ad clicks for the top ranked AdWords ad. Allows you to check for exact match, phrase match, or broad match.
Google Search Based Keyword Tool - shows keyword search volume estimates and keyword values by keyword, site, or category.