Eye on Idioms hosted by Read Write Think is a good site that students can use to practice identifying and using idioms. Eye on Idioms presents students with an incomplete sentence that they need to complete by selecting the proper idiom from a drop-down menu. To help student select the correct idiom, Eye on Idioms provides a picture hint. After selecting the correct idiom, Eye on Idioms asks students to answer a couple of short questions about the meaning of the idiom.
Eye on Idioms is available at http://www.readwritethink.org/files/resources/interactives/idioms/index.html