Apple has posted several sets of audio clips for iMovie 2 users.
Called "Sounds for your Scenes", the audio clips were provided by Killersound and SoundDogs. Killersound describes itself as a "music and sound design for new media" specialist. SoundDogs is a sound-effects and royalty free music library.
There are eleven music collections, and fourteen collections of sound effects – including weather sounds, doors, over a dozen bells, six animal sounds and even a set of spaceship noises for futuristic iMovie-makers.
The music collections include soundtracks for exotic travels, quiet contemplative collections - called Memories - offbeat, tribal and even techno sound tracks. All the collections are freely available for download from Apple.