And while I'm talking about Ubuntu Linux, I recently discovered a feature for Esperantistoj, courtesy of Mikeo of the Junularo Esperantista Brita (British Esperantists Young-persons' Group). Dankon! See the article for full details and other options.
For those unfamiliar, there are six letters found in Esperanto not found in other languages. This can complicate typing.
In short, System > Preferences > Keyboard > Layouts tab > Options button. Choose Adding Esperanto circumflexes.
Now, to get the point: just type the corresponding Latin letter while pressing the Alt key to the right of the space bar.