This is a great replacement for Microsoft Office for the person that's price conscious and still needs the functionality of Microsoft Office without the expensive price associated with it. Instead of Word you have Writer, Instead of Excel you have Calc, Instead of Power Point you have Impress, Instead of Paint you have Draw, Instead of Access you have Base.  You can open and save Microsoft compatible files.  If your looking to a cost effective alternative that has no cost than this is it. 

From OpenOffice: OpenOffice.org 3 is free software. That means you are free to download it, free to install it on as many PCs as you like, free to pass copies to as many people as you like. You may use OpenOffice.org 3 for any purpose without restriction: private, educational, public administration, commercial... Free, really free. Easy to choose, easy to install, easy to learn - OpenOffice.org 3 is the easy choice for an office software suite. OpenOffice.org 3 is suitable for complete beginners, but if you have used any other office software, that's ok too. OpenOffice.org 3 will make full use of what you already know - through familiar screens and menus - and also what you have - by reading existing files with no retyping. To download Open Office click the blue arrow below.