Whois

[boron]

WHOIS tells you basic data about domain, domain owner and hosting server. THere are many different WHOIS tools, which are pretty much the same, but I've found this one on Domaintools.com (http://domaintools.com) as the best so far.

It tells you:
- # of terms on the site, # of images, internal and outbound links
- listings in DMOZ, Yahoo dir. and Wikipedia
- IP adress and IP location
- personal data of domain owner
- basic data about hosting server (and hosting owner)
- clickable screenshot of your (or any other) site's Home page.

Here's WHOIS of Yahoo.com. Check (http://whois.domaintools.com/yahoo.com)

You can check PING, Traceroute, DNSLOOKup.

And there are other tools on that site...

[Submerge]

Use this site all the time, but i still access it through whois.sc

[boron]

Check if a domain or IP is on some spam list (http://www.completewhois.com/rbl_lookup.htm) (25 lists checked).

OPenRBL.org (http://openrbl.org/) looks in 39 lists.