You can find many good sources for learning idioms. Here are a few:
McGraw Hill's American Idioms Dictionary: This book contains over 14,000 idioms and their definitions. Purchase a copy.
Online Idiom Dictionaries: You can type in a phrase and find its meaning here.
Sites with idioms and quizzes for learning them: http://www.idiomconnection.com/
Lists of common idioms (web):
Simple list of 66 very common idioms.
A list of idioms and their origins.
A more comprehensive list.
To hear recordings of common idioms and use them for pronunciation practice, consider a subscription to our full online practice site.