Music : Aural & Theory Resources

Functional Ear Trainer 
Free software available for download, also available as an app for iOS & Android

Open Music Theory
A free, open-source, interactive, online textbook for college-level music theory courses

Toned Ear
Intervals, chords, scales, chord progressions, perfect pitch, scale degrees, intervals in context, melodic dictation.

Dave Conservatoire
Basic theory presented in a Khan academy style

e-Music Maestro
Sample aural tests based on the graded  ABRSM & Trinity examinations

musictheory.net
Comprehensive range of introductory and intermediate music theory lessons, exercises, and ear trainers. The creators of this site have also made this available as an iOS app, Tenuto

Teoria
Theory & ear training exercises for intervals, notes, chords, scales, melodies, rhythmic dictation, jazz.

Functional Ear Trainer
Free version available. Includes interval comparison, identifying intervals & chords, chord progressions, scales, note relative to chord, relative pitch.

Complete Ear Trainer
Includes intervals, scales, chords, inversions, chord progressions, melodic dictation.

Tenuto 
Theory & Aural in one app. Notes, intervals, scales, and chords.

Functional Ear Trainer
Includes interval comparison, identifying intervals & chords, chord progressions, scales, note relative to chord, relative pitch.

Rhythm Sight Reading Trainer
Improve your sight reading with immediate feedback of timing accuracy.

Perfect Ear - Music Theory, Ear & Rhythm Training
Includes intervals, scales, chords, chord progressions, melodic dictation, sight reading, note singing.