Office Suite - (Document Editor, Spreadsheet and Presentation Creator, MS-Office compatible) - OpenOffice

http://www.openoffice.org/ , http://contributing.openoffice.org

Browser/Mail tool - Firefox, Mozilla Suite, ThunderBird, Bugzilla

http://www.mozilla.org/ , http://www.mozilla.org/developer , http://www.mozilla.org/owners.html

Visual text file differencing and merging tool - WinMerge

http://winmerge.sourceforge.net/