LibreOffice is the top choice I think. It is free and easy.
Dido that! Libre Office is currently the best. It’s a shootoff of OpenOffice.org which was bought out.
OOo is in essence the same as Libre Office and what I used to use before it was bought. I haven’t touched it since it was bought.
I’m a software developer who daily uses Libre Office (on a linux box.)
I second GeronL on this. I've used pretty much all of them, was an OpenOffice devotee for years (and StarOffice before that) and I have NeoOffice on the Mac, but LibreOffice is the best at the moment.
Also seems to be the most compatible with real MS-Office, though none are perfect. Heck, even MS-Office N+1 isn't compatible with MS-Office N sometimes...