– One of the first places most people look, Whois will give you some basic information about the owner of the domain and where it is hosted. If the domain name isn’t currently registered you’ll simplify have the option to purchase it.
URL Trends – If the domain is existing, URL Trends will show some valuable information such as the PageRank, Alexa rank, and the number of incoming links recognized by search engines. The current data does not appear to be completely up-to-date.
Archive.org Way Back Machine – The most useful feature of the Way Back Machine is that it can show you when the domain was being used. Older domains benefit by having more trust from search engines (assuming they haven’t been penalized).
Domain History from Domain Tools – If you want to see if a domain name has any type of history, this is a good tool. Enter the domain and you’ll see dates in which the history is recorded. In order to see details you’ll have to upgrade, although it is free. If the domain has no history, you’ll see a message that there is no recorded history.
dnScoop – dnScoop has some different features than the other tools here, although it will also give you some of the same information. When you enter a domain it will tell you the age of the domain, the PageRank and Alexa rank, and the number of inbound links. One of the most useful features is that it will show you what other domains are hosted on the same IP address. Although if you purchase the domain you will be free to host it anywhere you choose.
dnScoop also gives you an idea of how much money a domain could make each month on Text Link Ads, which is obviously either an advertisement or an affiliate link. It will also calculate a value for the domain based on all of the information that it gathers. I would put too much weight into this value when deciding the price you should be willing to pay for a domain, but it can be helpful for comparing domains against each other.
Marketleap.com Link Popularity Tool – If you’re interested in seeing how many inbound links a domain has, this is a great tool. It will let you compare up to 4 different domains at one time. The report will produce the number of links being recognized by Google, MSN and Yahoo.
Google Banned Checker – You’ll want to avoid buying a domain that is banned by Google, unless you’re willing to work to get the ban removed. This tool will tell you is a domain has any pages indexed by Google. It is somewhat useful. If a domain has no pages indexed it is either new or banned. So, if you are buying a new domain this tool won’t have any value for you. Also, a domain can be penalized by Google without being completely removed from the index. This tool will not detect that penalty, it will simply tell you that a page is indexed.
SEOmoz Page Strength Tool – The page strength tool can be very helpful if you are evaluating a domain that has some history. It will show you a number of factors including PageRank, age of the domain, inbound links, and more.
Popuri.us – This is another tool for finding inbound links, rankings, and PageRank. It also includes a link to Whois and DNS info.
Number of Pages Indexed – If you are not sure whether a domain has a history or not, try this tool. It will show how many pages on this domain are indexed by the major search engines. If any pages are indexed there is some kind of history.