Top 15 Open source alternative to Microsoft products

Operating System	Windows	Ubuntu
Email Server	Exchange Server	Zimbra
Email Client	Outlook	Thunderbird
Browser	Internet Explorer	Firefox / Chrome
Directory Service / Identity Management	Active Directory	Open LDAP
Database	SQL Server	MySQL
Enterprise Search	Fast	Solr
Office Suite	MS Office	Open office / LibreOffice
Source code Management	Visual source safe / Team foundation	Git / Subversion
Web browser	IIS	Apache
Integrated Development Environment	Visual studio	Eclipse / Netbeans
Mobile OS	Windows Mobile	Android
Media player	Windows Media Player	VLC Media player / Zinf
UML and Network diagram tools	Visio	Dia / Star UML
Enterprise Content Management System	Sharepoint	Alfresco / Liferay