UPDATED (15 Jan 2009): Want Custom Logo on Loading without Jailbreaking iPhone Again?

Don't like the pineapple you get when you jailbreak your iPhone? Wanna restore it to the original apple or substitute it for your own logo? Here is the guide on how to do it
from ipod Touched:

http://ipodtouched.net/index.php?p=156

And another guide from Apple iPhone School:
http://www.appleiphoneschool.com/2008/05/21/changing-your-boot-logo-without-rejailbreaking/

Finally a guide on How To Change iPhone/ iPod Touch Boot Logo on firmware 2.0, 2.1 and 2.2 using Cydia App called LogoMe. This guide is a step by step with screen shots:

http://planet-iphones.com/2009/01/12/how-to-change-iphone-ipod-touch-boot-logo-on-firmware-2x/