Up to and including OOo 2, you can install new dictionaries for spellchecking, hyphenation and thesaurus, by opening a wizard document from the Files > Wizards menu.
In OpenOffice.org 3, dictionaries are installed as extensions.
- To find new dictionaries for OOo 3, choose Tools > Language > More Dictionaries Online. This opens your default web browser showing the dictionaries page.
- Select the dictionary you want and click the Get It button.
- Your browser displays a dialog where you can choose either to open the *.oxt file with OOo 3, or to save the file on your drive.
- Choose to open the file with OOo and click OK.
- This opens the Extension Manager and asks for your permission to install the dictionary. You might need to click the Extension Manager button in the taskbar to see this window. Click OK.
- Click Close to close the Extension Manager. Now it might be necessary to restart OOo 3, including to exit the Quickstarter, before you see the new dictionary.
Some more information about installing dictionaries for OOo 2 and 3 is here: http://extensions.services.openoffice.org/resources/user/howto_install.
The OOo Wiki has some dictionary information that may be important for users of OOo versions that are part of Linux distributions.
How about a grammar checker? Check the extensions web page for availability of a grammar checker in your language.