Gaslamp Computers

OpenOffice is a free and open source office suite produced by Sun.  It's main commercial competitor is Microsoft Office.

• Word Processor -  OpenOffice Writer :: Microsoft Word
• Spreadsheet -  OpenOffice Calc :: Microsoft Excel
• Presentation - OpenOffice Impress ::  Microsoft PowerPoint
• Database - OpenOffice Base :: Microsoft Access
• Drawing - OpenOffice Draw ::  Microsoft Publisher
• Math -  OpenOffice Math

Compatiblity

OpenOffice is fully compatible with Microsoft Office documents.  So if your friends create a document in Microsoft Office, you will be able to open and edit it in OpenOffice. 

Functionality

The functionality of the two suites is very similar.  Most people won't know even notice a difference because OpenOffice can do almost everything that Microsoft Office can.

Price

OpenOffice is free and all of the updates are free.  It can be installed on any computer for free.  Microsoft Office ranges in price from ~$100 for the Home and Student version to $500+ for the Enterprise version.  You'll also need a license for each computer.  In a business with 5 computers, OpenOffice can easily save you over $1000 compared to Microsoft Office.

Conclusion

OpenOffice is one of the most polished examples of open source software.  It offers all the functionality of Microsoft Office for free.  There is simply no reason to spend the money on Microsoft Office unless you're an enterprise user.

Software:

OpenOffice