Here are my picks for the Top Ten Domain Name Search Engines - there are a ton more than these ten out there, however, I've found these to be the ones that I've used most often and had the most success with. You can use these domain name search engines to check if a domain name you're considering is still available for purchase, or just to view domain name information.
"Search, look up, check, select, reserve, purchase, register, transfer, renew, protect, and / or monitor domain names, internet / Web addresses, or URLs for any country in the world from checkdomain.com." The search process here is very streamlined and easy to use.
Clickey does the standard domain name search, but also offers the option to view popular domain name searches on the front page, a nice feature. All countries are available to search for domain names, and you can also view contact info on a specific domain name by typing in "widget.com" to the search bar.
You can search for domain names here, but the real appeal of this site is that it lists all the domain name registries from all over the world. For example, did you know that Burundi's is .bi?
This is an interesting service - you can not only search for available domain names, but you can also see what's at auction or for sale if you're in the market to buy a domain name. Whois Source supports four different kinds of searches - IP address, partial words, full domain, and whois history.
ICANN, or the Internet Corporation for Names and Numbers, is not so much a domain name search engine, but more of an informational site about domain names and how they all got started. The ICANN Frequently Asked Questions should be your first stop when learning more about this organizational body.
Lots of different serives here at NIC; you can check WHOIS, view domain name registries from around the world, check out a nice set of domain name FAQ, and lots more.
Click on any of the geographic or generic extensions to search for domain names by country, or just use the general search bar to find an available domain name.
Just like ICANN, InterNIC is more of an informational site about domain names - what they are, how the work, how they got started, and more. This is a good hub of information that you might eventually need, such as how to submit a complaint about an accredited registrar.
Very deep site with lots to offer: domain name services, IP address services, protocol number assignment services, etc.
From the site: "Domain Hacks is a special domain name search utility. It results domain hack domain names, which are unconventional domain names like del.icio.us." This is a way to find out if specific domain hack names are already registered - and looks to be the only one of its kind on the Web.