The new book I Love It When You Talk Retro: Hoochie Coochie, Double Whammy, Drop a Dime, and the Forgotten Origins of American Speech by Ralph Keyes about slang sounds (and looks) great. You can read an interview with Keyes here. One fun nugget from the interview:
I was surprised to find out that there were no "secret decoder rings." There were secret decoder pins, but no rings.And the book is 34% off at Amazon.
There's also a blog at the NY Times devoted to interesting words and phrases. For example, bossnapping. Via.
*Previously: The origin of the word "scapegoat."
*Buy decoder pins at eBay.