http://nologo.sourceforge.net/index.html

Install this Java app, enter your phone number (only used to send yourself an SMS with the blank logo), pick your carrier (T-Mobile or Cingular are the only ones listed...not sure if it will work with other carriers), and hit send.

The great thing about it is that if you somehow lose the logo or reset the phone, you have the app to reinstall it...you dont have to try to remember how or where you got it. Super easy , ain't it??