There are a variety of open source consulting firms: (list alphabetically)

Asterisk IT

Specialists in develop, extending, deploying and maintaining the Asterisk PBX platform. Developers of AsterFax and The Receptionist Console

Link to AsteriskIT

Enomaly

A wide range of successful companies rely on Enomaly’s open source consulting experience to increase productivity, improve operational efficiency and reduce risk. Enomaly works closely with medium sized enterprises to plan, prepare, and coordinate achievable customer-specific content management and open source strategies. These tools effectively allow you to be more efficient and operate more successfully.

Using a web 2.0 service approach, enomaly offers a wide range of strategic services including ajax style application development, information/content management, open source migration support.

Enomaly will cost effectively guide you through each step to ensure that your completed project will attract principle customers, clients and business partners.

Link to Enomaly

Green Quadrant

Green Quadrant is a company specialising in sustainable and open source computing. We provide a broad range of services from IT strategy development to programme and project management, from process and solution design to software and hardware evaluation and deployment. All our solutions are implemented using open source software.

Link to Green Quadrant

InuXsys

Choose from open source ready-to-use application solutions for the most rapid implementation. Use them as is or as a starting point for customizing your own unique solution.

Link to InuXsys

HJK Solutions

HJK Solutions is an experienced operations consulting company that delivers infrastructures commonly needed by startups. Their expertise revolves around building the scalable systems every business must have to be competitive. By focusing on the technology, HJK Solutions enables companies to focus on building great products.

Most recent Launch: Avvo.com

Link to HJK Solutions

Optaros

Optaros is a consulting and systems integration firm that helps enterprises solve IT business problems by providing services and solutions that maximize the benefits of open source software.

Link to Optaros

Sirius Corporation

Sirius Corporation is one of Europe’s leading Open Source consultancies whose clients include some of the world’s best-known multi-nationals. Our mission is to make Open Source software available and affordable to organisations of all sizes, across Europe. We are a second generation Open Source consultancy that combines the cost savings benefits of Open Source with the methodologies, support, and accountability expected from an enterprise deployment specialist.

Link to Sirius Corporation

osRiver

osRiver is an enterprise consulting company who specializes in security and network management, UNIX technologies, and the integration of Open Source solutions. Our mission is to provide affordable, secure, and scalable solutions for our customers.

osRiver can help faciliate your projects using our own project-orientated methodology which incorporates several phases: information gathering, identifying software/hardware, application development, implementation, integration, and support.

Link to osRiver

northxsouth

northxsouth is an internet technology development and change management firm specializing in free and open source software. We have offices in San Francisco, California and Sao Paulo, Brazil and we work on projects in English, Spanish and Portuguese. Our experience comes from 10 years working in the trenches of the internet industry in Silicon Valley. We’ve not only built scalable web applications but also entire engineering departments with smoothly-running processes. Please take a look at our website to see the type of work we do.

Link to northxsouth

Webangel

Our mission is to bring open-source to the enterprises of Ireland and Europe, our offices are based in Dublin. We deliver scalable and extensible open source solutions. Our company is quite new on the market but our employees have a long record of successful open-source projects. For more information please visit our website.

Link to webangel

Openability.net

At Openability, our goal is to help you realize your Open Source strategy with Radview’s Award winning WebLOAD load testing tool. We believe that with us you can benefit both from an Open source world where load tools are affordable yet enjoy a top of the line professional services to support you’re testing needs

Link to Openability