Howjsay is a pronunciation dictionary of English words. This is a good web tool that you can use with students to help improve their English pronunciation.
With Howjsay, students will be able to look up the pronunciation of any word they stumble upon in their readings. The way it works is pretty simple: just type in the term you are looking for and hit browse. In the next page click on the mic icon next to that word and you will hear it pronounced for you.