Everyone knows that MS Office is the standard when it comes to an office suite, but that does not mean that it's the only office suite out there. One of the best alternative is OpenOffice.org. Aside from being free it has the ability to open MS Office files and edit them. The only setback is that that it can not save to the newer MS Office extension files like.docx files. Even with that limitation OpenOffice can save files to older versions of MS Office (2003 and under) without problems.
Comparison
OpenOffice.org MS Office
Writer Word
Calc Excel
Impress Powerpoint
Draw Visio
Base Access
------- Outlook
OpenOffice.org does not have an Outlook alternative but that can easily be taken care using other open source applications. Thanks to Thunderbird; an open source messaging application, sending and receiving emails will be easy. It's interface is similar to Outlook making it very user friendly. It is a full featured mailing application but as an upset, it does not have a built-in calendar feature.
Here comes Sunbird a very powerful calendar application. With Sunbird you will be able to keep track of all of your appointments and task. Like Thunderbird, it also has an interface similar to Outlook. There is also a project called Lightning. Lightning is a Thunderbird add-on that integrates Sunbird into Thunderbird. This makes Thunder even a better Outlook alternative, with the ability to not only send / receive emails, but also having power calendar features.
There are other free alternatives; but the ones above are the most popular ones.