iDeviceBrowser is an application that makes it possible for you to view and edit files on your iDevice (which includes the iPhone, iPod Touch, iPad, and Apple TV). In conjunction with "afc2add", which is available via Cydia, it allows access to the full file structure, or else just the /private/var/mobile/Media/" directory.
gcp (Goffi's CoPier) is a command line file copying tool, loosely inspired by cp, but with high level functionality like a progress indicator, the ability to continue copying multiple files even when there is a problem with one of them, and the use of a journal to track successful copying. File names can be fixed to ensure compatibility with the target filesystem. If you launch a copy operation when another is already running, the files are added to the first queue to avoid hard drive thrashing. You can keep track of files you have copied, and re-copy them later. gcp is approximately option-compatible with cp.