Asterisk

Asterisk is probably the most popular telephony system in the world. By decoupling PBX functionality from traditional purpose-built hardware and moving to commodity computer hardware, Asterisk reimagines what a PBX is.

FreePBX

Freepbx is a GUI that makes working with and administering Asterisk systems a breeze.

Flash Operator Panel 2

Flash Operator Panel 2 (fop2) is a browser-based operator panel for Asterisk and Freeswitch (another Open source PBX). Fop2 allows you to see at-a-glance the live status of your PBX, control calls, manage your queues, re-route calls, and integrate with CRM packages. If you have a call center or customer service department, having visibility is a key way to ensure your agents are servicing your customers efficiently and correctly.

Asteric

Asternic is a basic call center stats application that gives you moderate reporting capabilities on your Asterisk phone system. See quickly how your queue agents are performing and how to help improve that performance. They offer free basic reporting or slightly more advanced reporting for a nominal license fee.

QueueMetrics

QueueMetrics is a high-end queue reporting package that not only does queue reporting, but management of agents, agent grading, and customized reporting strategies to fit your needs. QueueMetrics is the most comprehensive Asterisk-based PBX reporting package out there.

OpenSIPS

OpenSIPS is an Open Source SIP proxy/server for voice, video, IM, presence and any other SIP extensions. It is used worldwide by large enterprises and voice carriers.

CGRateS

CGRateS is an offline / online rating engine used by telecoms and carriers for account balances, do least-cost-routing, and fraud detection, among other things.

Bandwidth

Telnyx

VoIP Innovations

Vitelity

Flowroute