I have found a large list of open source software on Windows, look at:

• http://www.opensourcewindows.org/
• http://www.opensourcewindows.org/page2.php

Before trying to master Linux, try to taste the open source products even on your current Windows operating system.

For server administrators, start using cygwin to experience the power of automating tedious tasks. There exist also tons of open source Java applications at http://java-source.net/