CheckYourNetwork.net - Free Online eMail Server Checking and Testing Tools

voip-calculator.com - Calculate VOIP Bandwidth etc.
    Voice over IP calculators for assisting in the technical design and analysis of VoIP

Bandwidth Checking Tools

 BandwidthPlace.com - Check your Connection Speed
    Check the Speed of your Internet Connection
Toast.net - Bandwidth Tests from various Locations
    Bandwidth Tests from various Locations
testmy.net - Checks Both Upload and Download Speed of your Network
    Checks Both Upload and Download Spped of your Network

Be Sure to Check out Clustered Networks Untangle Security Appliances

The Untangle Gateway, the world's first commercial-grade open source solution for blocking spam, spyware, viruses, adware and unwanted content on the network, provides a free and better alternative to costly, inflexible proprietary appliances. Untangle's applications are currently being used in tens of thousands of businesses in a variety of industries, including financial services, real estate, education, bio-science, and professional services.