Link Checking

Dead-links.com
Free online link checker. Spider-based technology and fast online analysis.
http://www.dead-links.com/

Free Link Checker For Webmasters
Link Checker is an essential utility for every webmaster who wishing to check internal and external links within their Internet site. Free check the validity of your links on any Web Page on the net.
http://www.indiabook.com/webmaster/link.html

HostPulse.com
Identify broken links in your site for free.The broken link checker will search your site, testing each link it finds and report the status of each link.
http://www.hostpulse.com/app/networktools/chklinkform.asp

Link Valet
Generates a color-coded report by spidering a site or checking links on a given page.
http://valet.htmlhelp.com/link.html

NetMechanic
Tune your web site with link validation. Robot will find broken links in your web site.
http://www.netmechanic.com/

View HTTP Request and Response Header
View request and response header of a HTTP connection and HTML source.
http://web-sniffer.net/

W3C Link Checker
This is a tool to get a deep information about links in a webpage, about errors and link inexistence.
http://validator.w3.org/checklink