OpenOffice.org 2.0 is an open, feature-rich multi-platform office productivity suite. The user interface and the functionality is very similar to other products in the market like Microsoft Office or Lotus SmartSuite, but in contrast to these commercial products OpenOffice.org is absolutely free.OOo 2.0 (oh-oh-oh two-point-oh... heh) is full-featured, and easily a Microsoft Office replacement.
I have nothing against Microsoft; frankly, I've been a fan of Microsoft Word since I first used it in junior high. However, OOo is free, cross-platform, and thoroughly equipped for every type of office work. If you already own Microsoft Office 2000 or newer, don't bother; if you are looking to acquire an office suite, OOo 2.0 is a great place to start.