These tools are extremely important in helping to find out how valuable a domain name is. Keyword research can give you a rough idea of how often a particular phrase is searched for at the top search engines. The Google keyword tool is one of my favorites, it tells you how strong the advertising competition is for a particular keyword or phrase - plus you can check the popularity of a keyword based on a language...
Pronounced as "who is", these sites/tools help you find out who owns a domain name as well as other vital domain registry information such as registration date, expiry date, last update, name servers etc. There are thousands of whois tools that provide more or less the same data - some provide more than others and present the information in different ways. Below I've listed the ones that I use the most... DomainTools...