Reverse Hash Calculator
The Internet Storm Center has a very intriguing tool called the reverse hash calculator, https://isc.sans.edu/tools/reversehash.html . On yhis site you can draw upon a database of millions of MD5 and SHA-1 hash values
Hash values are supposed to be one way functions - in theory you should not be able to work backwards from a hash value to the original string. The actual text of passwords are often not stored in databases in order to guard against a possible security breach. However with the Internet Storm Center you can decipher a large number of passwords. For example if you generate a hash value (on how to do this, see the Tip of the Night for December 5, 2015) for the string:
. . . you get the MD5 hash value, 4b3b429797098df347b00dd8875f153b , which can be decoded on the ISC site.