Andreas Marschall’s Toto® Tools

http://www.i-b-a-m.de/Andreas_Marschall%27s_Toto_Tools.htm is a collection of free, mostly TAPI related tools

ExceleTel TeleScope

ExceleTel TeleScope is a utility that can be used to test and learn about telephony devices and TAPI. You can find additional information and download at http://www.exceletel.com/.