Android: There are a plenty of office suites for Android. Few of them can serve as a direct replacement for the office software on your desktop, but AndrOpen arguably doesn’t need to — it’s a full port of OpenOffice.
The downsides to having a full OpenOffice port on your Android device are obvious: the UI probably won’t work very well on a phone (though it is technically supported). However, Android tablets can actually make fairly good PCs in a pinch. If you need a full office suite for a specific tablet task, AndrOpen is an impressive first effort.