With my experience I suggest to use Zoho (Zoho offers a suite of online web applications which is easy to collaborate. Zoho suite goes beyond that by offering a wiki, a planner, email , CRM etc..
Zoho provides a wide, integrated portfolio of rich online applications for businesses. With more than 20 different applications spanning Collaboration , Business and Productivity applications
The second choice is Google docs, Zoho is far better than google docs) In both you can create word processing documents, spreadsheets ,presentations and lot more. You can share these documents with friends and co-workers quite effectively with the push of a few buttons.
KOffice have distros for Windows, Mac OS X, Linux , there are eight packages in this suite, including project planning and image editing tools.
Lotus Symphony ,Libre Office,Abiword,Atlantis Nova ,SSuite Office and too many are in the list, but till this time MS office have one only competitor product , that is Zoho.
I am sure people have tried all most all these free suites to abandon MS Office, but the reality is, they always come back to MS office suites. The main reason for this trend is compatibility problems. So what we need along with Free Software and Open Source, we need Open Format in Software and in hardware too.