SamSpade
intoDNS
Squish
Pingability
DNS Check
DNS Report
Another DNS checker
DNS
Free online tools
Network Tools
Domain Tools
Reverse DNS
check
MX Toolbox
WhoIs
SPF Creator
SPF Record
Testing Tools
DNS BlackList checker
Multi-Realtime BlockList check
Multi RBL check
NJABL.Org
SpamHaus
Another list to check
Trend Micro
MAPS
blacklist lookup
SpamCop.Net
Reputation
Authority
MX ToolBox - also has additional tests
Shields Up
Symantec Security Check
Various
Online scanners
AuditMyPc
Sam Spade online tools
SubnetOnline
CentralOps Online
Webmaster Toolkit
Open port checkers
CanYouSeeMe
YouGetSignal
ShieldsUp
Internet Security
Blacklist Checkers