Following sites are the best ones that i decided to put here.
Sedo.com
Sedo.com is one of the biggest leading domain name parking program. You can simply park or sell your domains and obtain good profit. They pay monthly. If your profit is from domain sale then it is paid instantly.
GoDaddy.com
Godaddy.com is absolutely the biggest global domain registrar company. Their security policies are strictly executed. Their prices are extremely cheap. I suggest you to find some coupons before registering a domain.
Dnsstuff.com
Allows you to find the path of communication with the domain/ip that you specify.
Domaintools.com
They provide various paid and free information like whois, reverse ip etc. You can access many data at the same time.
Domainmeter.com
Domainmeter.com uses hundreds of variables to determine the value of a domain. You can assume the dm value as appraisal of a domain.
Alexa.com
Alexa provides detailed information on site traffic.
