Personal IP Telephony Gateway?
three55ml asks: "I'm interested in putting together a personal SMALL scale IP telephony gateway to the PSTN (telephone network). I have a server with a voice modem in the area code I want to make calls. Are there any solutions for Windows or Linux that let me integrate a simple voice modem and conferencing software to place calls via the Internet? I know about products like LineJack, but I would think using a simple voice modem this could be accomplished on this small of a level."
Do a search for H.323 (the protocol that VoIP uses) and you will find a lot of information. From what I have seen most of it for ISDN.
Google search
H.323 - ISDN Gateway
hmm... for fun I enjoy launching DDoS attacks against 127.87.42.5
Asterisk Open Source Private Branch Exchange (PBX) and general telephony toolkit
linuxtelephony.org
Freshmeat search
Good luck, and please report your findings to Slashdot!