AudioSlicer is a Cocoa GUI application that finds all silences in an audio file and allows you to split it into several smaller audio files and to name/tag them properly. For now only MP3 is supported but other audio formats may be added in the future.
(commercial) MidiYodi allows editing, examination, and playback of MIDI files. It contains an explorer which gathers a MIDI information summary from entire file collections and tools to edit and examine events and notes from individual tracks.
(shareware) lets you split huge MPEG-2 files in smaller chunks of size specified by user. It is also possible to extract a single segment of the file, given the starting and ending offset
Octave Shifter 2 is a free real-time pitch shifting audio effect for Apple's Audio Unit architecture. By leveraging existing technologies like CoreAudio, Altivec and SSE, Octave Shifter 2 offers a unique audio experience.
xEQ is a parametric EQ/Tone Control Audio Unit. It consists of Low and High shelf filters and three Peak/Cut filters. It is very useful for placing around distortion effects.