Below are some sites worth checking out. The first one is a demo of two software programs (for different levels of students) which can be purchased online (I'm not a marketer of this software, and watching the demo doesn't cost you anything, which is as far as I got). The great thing about this software is that the user can get visual and aural feedback of his/her own pronunciation, using software that produces a sound wave of the model speaker as well as the student's sample and allows the student to compare his/her sound wave file with that of the model. For low level learners, I like the minimal pairs practice at Many Things, but this site does not have video images so that a student can actually see someone saying the words or sounds. For free online viewing of English sounds, I highly recommend Jennifer's ESL site, which has a lot of helpful YouTube material. The only thing that is missing at these last two sites is a way for students to get feedback on their pronunciation. For this, students can always purchase a small hand-held digital tape recorder or download a free recorder for their computer from Audacity.
In addition, there are fun audio and audio-video recording sites which are free up to a certain number of megabytes (I'm giving you the homepage links), such as VoiceThread and Podomatic. You can sign up with e-mail and some basic information about the user. Instructors can also create sites where students can go and record themselves for feedback. I have not yet tried to use these last two devices for classes. I have had students do homework/quiz recordings using Audacity and e-mailing me their work as a wav or mp3 file. Voice Thread is perhaps an easier way for students and instructors to interact with each other aurally and visually. I am sure that many of my readers are experienced at Voice Thread or Podomatic already, so I welcome links and examples of how well it can work!