an good program would be open office witch can be found at openoffice.org but if you want the version that is still being developed by the community then http://www.libreoffice.org/ is the one to get this what i use now over open office as it still gets support. libreoffice is open office it just out in the open and not being sponsored by oracle so in my view libreoffice is the way to go its only going to get better over open office its self.
if you are using mac osx then off course you can use i work that can be found at
iWork is also an lot cheaper then Microsoft office its self and works great with mac makes using your mac easier when writting documents ect.
if you are looking for somthing that is web based that you might want to look at google docs or skydive by microsoft its self can be found at https://skydrive.live.com/ .
but having said that i like google docs more running with libreoffice dropbox or www.insynchq.com this way i can use powerful desktop software and my documents go with me where ever i go with google docs or with dropbox and i can still edit when on the move if need be that is what i use over Microsoft word, not sure what others think is better