I believe that Linux in the small business sector is a nice option. Many people would say that a windows server would be the way to go to handle a small office due to the ease of administration, and that would offset the licensing issues.

However, I would disagree, if the business' needs are right. I recently deployed a Linux SAMBA domain controller to a small business and it has been working flawlessly for about 6 months. Up for 50 days currently without a hitch, and it only goes down for upgrades.

Here is my reasoning: they do not need many of the advanced AD solutions that windows server family offers. The licensing for a windows server OS is extremely expensive. I already knew linux so there was no learning curve, and I was able to quickly set up a SAMBA server. I can also accomplish tasks pretty quickly with linux's many command line tools.

If you are a consultant and worried about the overhead of managing mutliple linux servers in small businesses, dont be. Linux is pretty easy to rollout in large numbers and manage. The package management solutions offered by the various distributions make mass updates and installations smooth. Also, things like redhat network make this idea on a large scale practicle.

In larger organizations, I would look at a heterogenious environment. Windows could be used to run RIS servers and AD servers if more advanced features are required, and for exchange. However, linux could be used to backend the file servers, and for web servers, database servers, dns servers, etc. Linux is extremely reliable and is good for getting the most out of your hardware and for critical applications.