Hey Whipple, Squeeze this! is one of my favourite books on advertising.
Whether you work for an agency or employ one you should read it. It will point out what you are doing wrong and show you how you can do things better.
It was written by Luke Sullivan, a copywriter with over 30 years experience working for some of the biggest agencies in the US.
It will make you laugh and cringe, particularly when he shares some painful examples of the stupid people he's had to work with (watch out for Mr. Froggy).
He doesn't talk much about charity advertising, but so much of what he says can be used to develop great fundraising materials.
Today on Adland I found a film of Luke presenting his thoughts on simplicity in advertising to a group of students. It runs for over an hour but should be considered required viewing for anyone whose job involves communicating with donors and working with agencies.