skAsterisk, a PBX, telephony engine, and telephony applications toolkit, is one of open source best-kept secrets. As with many open source projects, there is a company that has been set up to provide support, Digium.

Here's its latest press release:

Asterisk bills itself as "the world's leading open source PBX, telephony engine, and telephony applications toolkit." You can use it as the basis of a fully featured, enterprise-class phone system in your organization.

Asterisk is the world's leading open-source PBX, telephony engine, and telephony applications toolkit with immense flexibility. 'Asterisk Gateway Interface 1.4 and 1.6 Programming' book by 'Nir Simionovich' will give you a firm understanding of Asterisk Gateway Interface (AGI) development and proper AGI development practices.

When Asterisk sponsor Digium, Inc. released AsteriskNOW, early in January 2007, the stated aim was to provide an open-source telephony "appliance." Not appliance as in hardware/software combo, but appliance as in 'all the software you need to get a complete telephony application up and running'—even if you don't know a lot about Linux administration.

Mark Spencer never expected to be where he is today, but the Auburn, Ala., native is making a name for himself in the world of technology.

In addition to the well-known Asterisk, there is a vibrant community of open source software PABX systems that can be used for internal and service provider IP telephony.

Some critics say Asterisk — the open source IP PBX — is for hackers rather than real telephony customers. EUS Networks begs to differ. The New York-based solutions provider, which works closely with Digium, has launched an Asterisk-based IP telephony solution for a hedge fund client’s trading room floors. Here’s the scoop.

A quiet revolution continues at Digium, the poster child for Asterisk — the open source IP PBX platform. Many open source companies struggle to line up resellers and solutions providers because, frankly, it’s unclear how to profit from open source. But in Digium’s case, more than 250 partners are banging on the company’s door because Digium really has built a better mouse trap.

Asterisk is one of the best telephony solutions which is free to use. There are others such as yate that provide same type of solutions and even more custom ones. Due to the easy of implementation Asterisk has become more popular than anything else. Asterisk is very easy to use and lots of open source and closed source panels provide a GUI for it.