I just found this useful page about Japanese Slang and Colloquialisms, Japanese Idioms, Japanese Proverbs and Sayings.
Thanks to Language Realm
Japanese Slang and Colloquialisms – Like all people, the Japanese have a wide variety of earthy, pithy, and even rough and rude ways of talking about life. Covered here are the words and phrases often ignored in dictionaries, and often unacknowledged by the Japanese themselves.
Japanese Idioms – A collection of common idioms, from the formal to the colloquial and regional, with romanized versions for people who don’t read Japanese, and natural English translations and explanations.
Japanese Proverbs and Sayings – A practical, complete guide to the many proverbs and sayings used in the modern language. Newspapers, speeches, even television and movie dialog routinely use these, so knowing them is vital.