Do you like the purist sound, or correct for vibrations in your car. Maybe you have assymetric hearing loss and need to eq the left and right ear differently.
Equalizer - Enhance your music in your music library on your device. Manual here
CloudEQ - Enhance music from the cloud (SoundCloud and Dropbox, for now)
Links to audioforge.net (2)
audioforge.orgAudioforge Labs Inc. - iPhone, iPod touch and iPad apps for music manipulation
audioforge.caAudioforge Labs Inc. - iPhone, iPod touch and iPad apps for music manipulation