KeePass for BlackBerry is MUCH better than RIM's Password Keeper and because it's also available for pretty much everything else (Apple Mac OS X, Linux, Microsoft Windows, Java-enabled devices and Microsoft Windows Mobile), you can easily keep your data in sync between multiple platforms!
It's Open Source (ie. Free), data is more logically organized, it's ridiciously secure due to the VERY high-level encryption standards supported and very memory-friendly on all platforms.
VERY, VERY highly recommended...
KeePass Password Safe
The link above takes you to the Windows version, but there are links on this page to the other versions, and I believe that the BlackBerry version IS AVAILABLE OVER-THE-AIR (ie. You can download it DIRECTLY to your device, without the use of a computer), as are most versions...
Posted from my CrackBerry at wapforums.crackberry.com