Well there is Documents (Office Docs) it works on the iPad and iPhone and also works on windows and Mac.
Documents by SavySoda™ ••• Reached #1 overall BUSINESS APP ••• ••• on App Store in OVER 40 COUNTRIES. ••• ••• Over 30 Million Users on iOS ••• ••• AS FEATURED BY APPLE, USA TODAY ••• iPhone's and iPad's lightweight mobile office suite. This essential application allows you to edit and...
apps.apple.com
Well not sure if it is free or not.
It similar to Microsoft office or iWorks may not be as feature rich but doing basic task it probably be just as good.
Again not sure if it is free or not but base on that page it looks like it is cross platform forum support.
Not sure if anyone here usesd it or Zoho?