ESLvideo.com

This site primarily seems to use YouTube videos, the quality of which, obviously, vary greatly. They seem to have been graded, but it's not clear how the grading works or how accurate it is. The exercises are also mostly of dubious value. Overall, if you find something useful, that's great, but perhaps the best part of this is the ability to make your own exercises. It requires a login, but the account is free.

Cambridge Student Arcades

Cambridge University Press publishes many ESL textbooks, and they're putting a lot of the related audio on the web for anyone to download. They also have specific listening exercises for many of the chapters. Go to their Student Arcades page and select one of the textbooks and then the book level (most of the books would be for lower-level EAP classes.) Next, either download self-study audio, or click on "sort by activity type". The listening exercises are called "What do you hear?"

Dictation

Dictation is a good way to focus students on the details of language form rather than meaning. Of course, looking at form without understanding meaning impoverishes language learning, but an unrelenting focus on meaning can distract attention from form and slow learning. One site that provides dictation practice is Listen and Write. It requires students to create an account and log in, but it is free.

It has a number of levels and a level test. The levels test is in beta, and I was placed in level 6 of 10 (based on the graph) despite doing the test in earnest (Also, confusingly, the audio seems to go up to level 22). I think the problem may be that I was hitting punctuation where none was expected and then barrelling on past the error with each keystroke counting as a further error. I'm not really sure though.

Another thing to be careful of is that not all of the tracks are English, so look at the language label. Also, the audio quality varies. All in all, it's may be a good idea to vet a number of dictations yourself before sending your students to the site.