Direct download (i.e. from Apple servers) links for officially-released iOS firmware versions through 6.1.4 are listed here, with checksums:
These firmware images can be used to do a restore within iTunes (option-click the "Restore" button) without downloading the firmware via iTunes, e.g. if you have several devices to restore on different computers or if the computer running iTunes is not as well-connected as another available computer.
What, if they exist, are the direct download links for iOS 7.0?