Here are 10 useful Free Open Source Office - Business tools to replace MS Word, MS Excel, Access. create PDF files, etc.

1. PDFCreator: You can create PDF files using any program.
2. Abiword: Free word processing program to replace MSWord. Available also for Linux and Mac OS.
3. OFBiz: Open Source E-Bussines.
4. MySql: The most popular open source database.
5. PostgreSQL: A powerful database. You can administrate databases with millions of records and 400+ Gb of data.
6. OpenOffice: Free Open Source Office Suite to replace MS Office.
7. Sunbird: Calendar application that you can use around the world. By Mozilla.
8. Gnome Project: All tools for Gnome.
9. TimeStamp: Use this tool to track time spent on a project.
10. Power Talk: Free program that automatically speaks any presentation or slide show running in Microsoft PowerPoint for Windows.

Enjoy!!

Also, you can see 10 Free Open Source Video Tools

If you know another free Open Office Tool, please share it.