While everyone is talking about VoIP,
http://www.asterisk.org/
If your a company it may save you some $$ if you have remote sales people. Basically you can take POTs (standard phone lines) or even the higher grade lines (T1s and such) and turn it over to VoIP. Its an open source
I am suprised its not more popular in this community as everyone seems to travel alot. You can use a softphone (software) or even the hard phones (such as the cisco phones) and log in from your hotel rooms (bandwidth available that is).
This is likly more than you want, but its a possibility.
-Deek
3420164