Direct download (i.e. from Apple servers) links for officially-released iOS firmware versions through 6.1.4 are listed here, with checksums:
http://theiphonewiki.com/wiki/Firmware
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?
Best Answer
I found the direct download links for .ipsw files from Redmond Pie's very helpful post.
The links below are for build 11A465 of iOS 7.0:
Should you be a reviewer or get lucky with an early delivery, the 5c and 5s firmware update - build 11A470a of iOS 7.0.1 are below courtesy of an article by Mike Webb on mobilespie:
Also, I'd kindly remind people to not be greedy - downloading all the builds means someone else looking for one build might be prevented from getting a download.