Companies that embrace Open Source Software commonly use the following, what I call, first tier open source applications:
8. Magento Commerce (soon)
Some others - Asterisk, Joomla, Drupal, and maybe some day OrangeHRM
All of these applications can be used in the enterprise, depending on your needs and type of business. The more integration offerings between these applications, the better everyone will be including the open source companies - due to the added exposure.
It is difficult to condition employees to use various applications which is why integration between some of these applications is so critical.
This is one reason I do not like offerings that are similar. For instance, lets look at document storage and sharing.
Alfresco is the true enterprise content management application, however, both Zimbra & SugarCRM offer this functionality.
This results in users using all three. Yes, I can disable this functionality in Zimbra and SugarCRM, however, I do not want to do this until I know what makes the most sense. Maybe we don't need Alfresco? But maybe we will grow into a robust document management application.
These are just some of my thoughts. It would be great to see some of these companies work with each other in the integrations which will allow for supported integrations.