For server operating systems, we strongly recommend the SuSE Linux suite. For data storage/database applications, we normally use Progress for large mission-critical solutions, or Microsoft Access for PC/Windows-based ones. If an application needs a data/web interface or an e-commerce store, we recommend Miva/Mivascript, or for an Open Source solution, a combination of PhP and MySQL.
If your organization needs industrial-strength fax software, HylaFAX is the answer. This product is designed to work with Linux servers.