Soaring on Ridgelift: Open Source Company List

Applications
XWiki - Wiki Application

Business Process
Intalio - BPM tools
Pentaho - BI platform

Compatability Tools
CodeWeavers - Tools to run Windows apps on Linux

Consumer Electronics
Neuros - Media players
SlimDevices - Audio media players

Content Management
Alfresco - Enterprise content management solutions
eZSystems
Infrae
Nuxeo
Zope

CRM
SugarCRM - Customer Relationship Management solutions

Database
db4Objects - Object database for Java and .NET
EnterpriseDB - RDBMS based on PostgreSQL
GreenPlum - Database servers for business intelligence
Ingres - RDBMS based on Ingres
MySQL - MySQL RDBMS
Sleepycat Software - RDBMS based ob Berkeley DB (now part of Oracle)

Developer Support
ActiveState - Open source language tools (Perl, PHP, etc)
CollabNet - On-demand collaboration tools for distributed development
GlassBox - Diagnostic tools for Java programmers
Koders - Search for Open Source software
Krugle - Search for Open Source software

Document Management
KnowledgeTree - Document management system

Embedded System Support
Montavista Software - Linux distribution for intelligent devices & infrastructure
TimeSys - Tools for custom embedded Linux distribution
TrollTech - Tools for Enterprise & portable devices device applications

Enterprise Application Support
OpenLogic - Infrastructure management tools and certified library of Open Source apps
Optaros - Consulting & integration services for Enterprise apps built on Open Source
SourceLabs - Support services for certified stacks of Open Source software
SpikeSource - Certified Open Source stacks and applications
Univa - Enterprise version of Globus grid software
XenSource - Enterprise version of Xen Virtualization software
Zend - Tools to deploy & maintain PHP applications

ERP
Compiere - ERP applications with integrated CRM
OpenPro - Licensed ERP applications built on Open Source

Intellectual Property Management
BlackDuck Software - Compliance management tools to detect use of Open Source
Palamida - IP management for Open and Closed Source

IT Management
ActiveGrid - Management tools for LAMP applications
FiveRuns - Systems Management
GroundWork Open Source - Management and monitoring of IT infrastructure
Hyperic - Monitor & control IT infrastructure
Qlusters - Software to automate Enterprise Data Centers
Zenoss - Enterprise IT management system
Zmanda - Data protection solutions for backup and restore

Linux Distributions
Canonical - Ubuntu Linux for desktop and enterprise
Linspire - Desktop
Mandriva - Desktop & Enterprise
Miracle Linux - Miracle distribution
Red Flag - Asiaux distribution
Red Hat - Desktop & Enterprise
SunWah
Xandros - Desktop

Messaging
Collax - Enterprise/SME messaging and security
Funambol - Push email to mobile devices
MuleSource - Enterprise Service Bus messaging framework based on Mule
Scalix - Messaging infrastructure platform
SendMail - Enterprise messaging products
Zimbra - Enterprise messaging

Network Software
OpenClovis - Platform software for carrier grade telco systems
Vyatta - Network Infrastructure software for routers & switches

Report Writer
JasperSoft - Report Generator

Security
SourceFire - Network security products based on Snort

SOA
LogicBlaze - Enterprise SOA platform

Telephony
Digium - Asterisk Open Source PBX

Criteria for adding a company to the list are;
Must have a commercial purpose - whether selling software licenses or providing support and enhancement services.
Offer downloads of their software (including source) under either the GPL or their own versions of an Open Source license.
Must have a product offering - pure consulting companies are not included