http://www.i-b-a-m.de/Andreas_Marschall%27s_Toto_Tools.htm is a collection of free, mostly TAPI related tools
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/.
Tapitest is a free application including source written in Delphi 7. It demonstrates how to use TAPI 2 function calls. It contains the most basic functions needed when you start with TAPI. You can download the executable including source at http://www.mestdagh.biz/freeware_files/tapitest.zip