(for Del Williams @delwilliams on Twitter)

Tiggers by Joseph Sugarman

The Adweek Copywriting Handbook by Joseph Sugarman

Advertising Secrets of the Written Word, by Joseph Sugarman

My Life in Advertising and Scientific Advertising by Claude C. Hopkins

How to Make Your Advertising Make Money by John Caples

Tested Advertising Methods by John Caples

Persuading on Paper by Marcia Yudkin

The Copywriter's Handbook by Bob Bly

The Accelerated Program for Six-Figure Copywriting by American Writers & Artists, Inc.

On the Art of Writing Copy by Herschell Gordon Lewis

Direct Mail Copy that Sells by Herschell Gordon Lewis

Hypnotic Writing by Joe Vitale

On Writing by Stephen King (yep, THAT Stephen King; though I'm not at all into horror, I am impressed with King's book on writing)

Stein on Writing by Sol Stein

and anything you can get by Dan Kennedy of Phoenix, Arizona