The importance of backing up your data cannot be overstated, nor can the importance of a good storage card backup utility. The best I've found is Pocket Backup Plus 2.0 from Sprite Software (www.spritesoftware.com). This software suite includes Pocket Backup 2.0 and a number of features that make it my number-one backup program:
Self-extracting restore files. This feature lets you create stand-alone backup files you can use to restore your system without having to reinstall Pocket Backup. For example, if your batteries have died or if you've had to do a hard reset, insert the CF or SD card with the self-extracting backup file into your Pocket PC, use File Explorer to find it, tap on it, and it will completely restore your Pocket PC's system.
Automatic backup with a low battery. When enabled, this feature automatically backs up your data when your battery level falls below a user-defined threshold. The program continues to monitor your battery even when the Pocket PC is switched off. This means that you can leave your Pocket PC behind in your drawer when you go away for a long weekend, and as long as you've got a storage card in the slot, you don't have to worry about losing important data.

The Battery Monitoring feature automatically backs up your data when your battery level falls below a user-defined threshold.
Scheduled backups. You can schedule an automatic backup on a once-only, daily, or weekly basis.
Selective file and folder backup and restore. Pocket Backup gives you complete control over what is included in a backup. For example, you can choose to back up only your My Documents folder, or any other set of files or folders. You can also create a list of files and folders to exclude from your backup. At restore time you can choose to restore just a single file, or an entire folder, or multiple files or folders.
Selective database backup and restore. The Pocket Outlook databases can be selectively included in any backup or restore. So, for example, if you haven't backed up for a while, you may want to restore just the Contacts, rather than the entire system. Or you may want to restore the entire system but not the appointments database, which would probably be out of date.

Pocket Backup 2.0 lets you selectively back up and restore Pocket Outlook and other database files. (Note: You can also back up directly to a PC, without using a storage card, and restore without using ActiveSync by using PC Agent, which comes with Pocket Backup Plus 2.0.)
PocketMon and Space Detective
Pocket Backup Plus includes two additional utilities and a special feature:
PocketMon is a handy Today screen plug-in that displays your battery level, available program and storage memory, and a CPU usage monitor. It tells you when the last backup was performed and when the next backup is scheduled, and indicates the status of the backup.
Space Detective is a storage analyzer utility that provides an instant summary of how the storage space on your Pocket PC is being used. It's simple to use, provides information on the database files, and helps you keep your Pocket PC free of clutter and running at peak performance.
The latest version of Pocket Backup also comes with a PC component that lets you backup to and restore from a PC or network--up to 20 times faster than Active Sync. This PC component supports backup via cradle or wirelessly, to PC or network shared folder. You can initiate the backup from either the Pocket PC or the PC. If your batteries ever die, or if you have to do a hard reset, a restore initiated from the PC is the fastest way to get up and running.
Not much left to improve upon