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(in no particular order and under construction, of course)

Voice over IP calculator
Offers free VoIP resources, white papers, a directory and a forum

IPxStream
Voice and Fax over IP News and Marketplace

A ton of resources on voice over Internet Protocol including history, benefits, security, etc

NetworkWorldFusion Research
Primers and tutorials, Major aggregate sites of VoIP resources, Case studies, Newsletters and other online periodicals, Conferences

VoipSurvival 
offers free VoIP resources, including white papers and a directory. This site 
explains VoIP without geek speek. Don't let that fool you, the subject 
is well covered, and all of your questions will be answered. 

Jeff Pulver's Voice of Telephony

Iptelephony.org

Voice over IP - Per Call Bandwidth Consumption:

http://www.cisco.com/warp/customer/788/pkt-voice-general/bwidth_consume.html
(available to registered users)

http://www.cisco.com/en/US/tech/tk652/tk698/technologies_tech_note09186a0080094ae2.shtml
(available to non-registered users)

Troubleshoot & Debug VoIP Calls - the Basics:

http://www.cisco.com/warp/customer/788/voip/voip_debugcalls.html
(available to registered users)

http://www.cisco.com/en/US/tech/tk1077/technologies_tech_note09186a0080094045.shtml
(available to non-registered users)

Click here for Heinz Ulm's home

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