ImageUSB is a free portable tool for backing up, copying, cloning and otherwise working with USB flash drives.
The program can write .iso, .bin and .img images to multiple USB drives simultaneously, great for bulk copying operations.
ImageUSB can also create exact bit-level image backups of your drives, securely wipe or reformat them. (We didn't test the reformatting operation, but the developer claims it works with "even hard to format drives".)
All this functionality is presented in a straightforward interface which generally works just as you'd expect. Choose one or more drives, select an operation, click Write/ Create/ Zero/ Reformat and watch as the program goes to work.
There's a problem? ImageUSB can help even here, thanks to an on-screen log. If it doesn't display a USB drive on launch, for example, just glance at the log box and you'll see the drives it's checked and any errors that came up.