Asterisk lets you manage your phones. You can set up extensions, letting phones call each other. You can also set up routes out — connections to other offices, to the public telephone network (PSTN), or to other VOIP users. You can hook to the PSTN with either a $10 hardware device, or by using one of the many cheap VOIP providers, or whatever. And you can set up automatic call routing rules — for instance, you might route local calls over your local PSTN link, but fall back to a VOIP provider if your local link is in use.
Here are some links for Asterisk information:
- The Asterisk wiki, an excellent resource
- VOIP phones, hardware phones that take an Ethernet cable, or software phonse that run on a PC
- VOIP service providers, listing some free IP-to-IP VOIP providers, as well as VOIP-to-PSTN and PSTN-to-VOIP companies.
- FreeWorld Dialup is an excellent free VOIP-to-VOIP provider. They also have peering with many other VOIP networks; you can, for instance, call Vonage customers for free via FWD. FWD also has a free link to the PSTN for calling toll-free numbers in several countries.
- VoipJet lets you call anywhere in the USA for 1.3 cents per minute, and LiveVOIP does the same for 1.2 cents per minute. With LiveVOIP, you can also purchase a phone number for incoming calls for $4 to $8 per month.
- IPkall gives you a free local number in Washington state that forwards calls to your FWD account. There are some other companies that do similar things, too. Many also have very low rates on incoming toll-free calls.
- Asterisk tips and tricks is a great page
- Asterisk Handbook Project
- Asterisk Documentation Project