(commercial) Use Airfoil to send any audio to the AirPort Express, or multiple units simultaneously. Get the ultimate AirPort Express experience
(commercial) iCaption is a simple-to-use soft subtitle editor, utilizing timeline based editing. Soft subs are files stored separately from the video file, rendered in real-time as the video plays.
MpcOSX is a native client for MPD, a jukebox that supports all sorts of clients and file types. It lets you browse the library, add tracks to playlists, save playlists, skip around between or inside tracks.
MusicWatcher is a native OS X application written in Cocoa for doing real-time and non-real-time music analysis, visualization, and animation.