Good Ear - Contains solfège mapping, interval identification, and cadence identification. Allows students to track their progress.
Online Ear Trainer - Tests interval and chord identification at varying degrees of difficulty.
Ricci Adams' MusicTheory.net - Contains interval and chord identification, as well as some resources that may be useful for written theory.
Teoria - Includes interval identification as well as melodic, harmonic, and rhythmic dictation. Be sure to stay within "diatonic harmony" on the website for MUSC1121.
The Musical Mind - Tests interval identification, melodic dictation, and is especially good for solfège mapping. Students should use the "traditional names" option when drilling intervals.
SolFi Ear Trainer - Note that this site contains an app available for download to iPhones or iPads only. Tests interval and chord identification, as well as melodic dictation.