AptBackup is an application in Cydia that will make a backup of your Cydia installed apps, it does not make a backup of your actual applications or settings. It will make a list of everything you installed from Cydia and back that up. When you restore, it will reinstall all the packages in one step. The list is stored with other settings files and backed up with iTunes. When upgrading to 2.1 you can rapidly restore back your apps etc…although if you have a lot of apps and themes it could take some time.
» Cydia – AptBackup 1.1-3