Resources of Various Web Tools | Learn Web Design Online .com

xml-sitemaps.com - generate XML sitemap for your website. Nothing to install. Enter the URL and set some options.
Alexa.com - see traffic rank and number of incoming links
The Way Back Machine -- see how website looked in the past.
Google Webmaster Tools
Webmaster-toolkit.com
DomainTools.com
Accredited Registrar Directory
TheFreeCountry - list of free webmaster resources
DNSstuff.com - health check of your domain name
QualifiedAddress.com - web service to validate and scrub user inputted addresses
DimDim - collaborative online meetings and desktop shares
Senduit - Transmit large files to each other
Etherpad - Online collaborative document edit. Has a chat room as well.
Rex Swain's HTTP Viewer - Enter URL and see the head and text content returned.
ConceptShare - upload and share design spec for multiple user collaboration. CorelDrawConceptShare is a branded version of ConceptShare. They both have free trials.
Infinovision - adds streaming video to your website.
BackLinkWatch.com - checks the backlinks to your site.
DownForEveryoneOrJustMe.com -- tells you whether a site is up or down
Proxify.com - web based anonymous proxy service to let you surf the web via an intermediary proxy even if your firewall blocks a particular site.

Email Newsletter Services

MailChimp.com - has free option, pay-as-you-go option, and monthly pricing plans
ConstantContact.com
iContact.com

Tools to Tests Whether Site contains MalWare

McAfee SiteAdvisor - enter the domain name and it will tell you if a site is a phishing or spam site.
StopBadWare.org Report Search - enter URL and is if it is listed in the bad website clearinghouse. Their request for review form in case your site was listed due to hack.
Norton's SafeWeb
UnmaskParasites.com - search page content for any malicious content

If you site has been hacked and got listed in any of the above, this article explains how to fix and this article explains what you can do to get removed from the listing.

You can report malicious site to Google here.

Besides Norton and McAfee, you can try ESET NOD32 anti-virus or the free AVG Anti-virus.