http://www.anti-abuse.org/multi-rbl-check/

• email
• check
• spam
• list
• RBL

http://www.shellcheck.net/

• shell
• bash
• tools
• linux
• commandline
• development
• check
• checker
• lint
• webapps

http://www.allaboutspam.com/

• check
• test
• mail
• email
• spam

http://www.mozilla.com/en-US/plugincheck/

• firefox
• plugin
• check
• updates

http://www.ud.com/

• brand
• availability
• branding
• domains
• identity
• socialmedia
• social
• internet
• check

http://namechk.com/

• username
• socialnetworking
• check
• name
• namecheck
• community