Despite the oo website saying that the Australian dictionary is include in OO 3.x.x I couldn't spell check my docs.

The "Text Language" field of the OpenOffice Spell Checking dialog was missing.

So I had to download the OpenOffice Australian Dictionary and install it by clicking Tools ==> Extenion Manager... ==> Add...

Restart OO when you have installed the dictionary

You can tell when you have the dictionary for your language installed because it will have an ABC with a blue tick beside it:

The above is regarding OpenOffice 3.2 on Ubuntu 10.04 which has been upgraded from 9.10 but a has new user profile (i.e my home directory doesn't have any old stale oo settings that I know of).