Cracking, or jailbreaking your iPod or iPhone gives you access to dozens of free apps that aren't available on the standard issue iPods and iPhones. However, because you cracked the device, iTunes won't recognise your apps as having been paid for. This means you can't back them up properly. If your device were to crash, you would lose everything, with no way to restore it. However, there is a way to sync your cracked apps to your iTunes, backing up all of your apps. Please be cautioned however, that cracking your iPod or iPhone will void the device's warranty.
Open the Cydia program on your jailbroken iPod or iPhone.
Touch "Manage" > "Sources > "Edit > "Add". Type in the following address: http://cydia.hackulo.us. Touch "Add Source" when you're finished typing in the address.
Navigate back to the Cydia home page and type "AppSync for OS 3.0" (or AppSync for OS 4.0 if you have the 4.0 software).
Install the application when prompted, and touch "Confirm" to continue.
Connect your iPod to your computer via its USB cable and open iTunes.
Check the boxes next to the apps that you want to sync and click the "Sync" button. Your cracked apps are now safely backed up to iTunes.