Hmm. Various other plug-ins but nothing about java. Will try Brett's suggestion. But after I've posted about something else. (Having a bit of a day of it.)
Bev, try visiting about:plugins (that is, type about:plugins into FF's location bar) and see if the Java plugin is mentioned.
You can try installing sun-java6-plugin (as Brett said) which pulls in all the required dependencies. Alternatively, you can try installing icedtea-plugin which uses OpenJDK rather than Sun's JRE.