COCA

http://www.visual-idioms.com/

This can be done as a revision activity or before presenting selected idioms. It should be done at a language laboratory with computers or on students' tablets. Put the following chunks on the board:
 
the bottom of
stop at
be in the
take care of
be on the
run into
 
Students go to COCA (Corpus of Contemporary American English) and type in the phrases above. This is a great tutorial by Scott Thornbury on how to use COCA: http://scottthornbury.wordpress.com/2013/05/12/c-is-for-coca-corpus/

The task is to find some of the most frequent collocations. For example, for stop at students will get stop at + store, stop at + point, stop at nothing, etc. For the bottom of they'll get the bottom of the stairs (screen, sea, and barrel).
A) If you are doing this activity before presenting new idioms (stop at nothing and scrape the bottom of the barrel), you can direct your students to get to the words you need. To do this, you can show them the image and ask them to select the corresponding word(s) from the list of collocates. So if you need to teach scrape the bottom of the barrel, you'll just show the image of the barrel (http://visualidioms.blogspot.cz/2013/08/scrape-bottom-of-barrel.html). Working with the corpus, students will be able to see all the example sentences with the idiom and how frequent it is.
B) If you are doing this after you've presented your students with the idioms, this can be a vocabulary expansion activity: students look for more collocates of the words they already know from the idioms. They will be able to see how clearly English language is patterned.