The Market page for BootFlash Pro is here.
Also available on the Android Market is BootFlash Lite.
Here is the description from the Android Market.
BootFlash Pro lets you choose an image stored on your phone to install as your rooted phone's splash screen. The splash screen is the image that is displayed on your screen when you turn on the phone before the boot animation begins to play. The splash screen installed by BootFlash Pro will stick across different ROMs, so that you can always retain the splash screen that you enjoy. You can change your splash screen as often as you want.
BootFlash Pro currently works on:
HTC Inspire 4G
HTC Desire HD
HTC Desire Z
Edit: Added support for HTC Droid Incredible and HTC Evo 4G
and more to come!
Please do not attempt to use BootFlash Pro on any phone not listed here.
Edit: Force close issues on choosing an image have been fixed!