Been looking around and found link to a list online
Looking at openoffice and libreoffice mainly because I have heard of them before.
My main concern is formatting being messed up when converting between Word and alternative (and sometimes back again).
I’ve heard great things about OpenOffice, though I haven’t used it enough to tell you if it will be messed up when converting between Word / Alternatives.
Both Microsoft (Office) and Google (Docs) have online versions of their programs. They’re both pretty great, offering Excel / Spreadsheets as well as their normal Document programs. Personally, I prefer Microsoft’s Word Online, because it has most all the features installed Word does.
Word online you have to pay for it, I believe. Noticed in my search that you can get microsoft office free if you have a valid student email.
I have tried googledocs with Word but messes up formatt. There is also an ability to edit actual Word documents (as Word) but you hve to convert to download … cue mess. 
[spoiler]The truth is…
Even different Word versions mess up with themselves.
If this is really important, you need to stick to a single program version and format…
Sorry, but this is true.[/spoiler]
When I first saw the title of the topic, I thought it was a spam bot.