Apart from doing films, Bill Nighy has done a lot of other things too, including Theatre and radio work. Information about some of his work can be found here, but it is far from complete. It will however be updated and extended along the way.
Bill Nighy has done hundreds of radioplays for the BBC, and it will probably be impossible to list them all her. Some of the are available on tape through BBC, and BBC7 regulary broadcasts some of them.
Anyway : Radiowork (a pathetically short list at this moment, but will be updated eventually)
A list of Audiobooks Bill Nighy has done.
Theatre work (fairly complete)
Narrating work (not complete)