Starting with the release of iOS 4.0, Apple is rolling out all iOS updates for free, regardless of the device type. Now, iPhone and iPod touch owners alike can freely download iOS IPSWs (software update files) and selectively restore their devices to them whenever they wish. iPad users also download their firmware updates for free. The tablet’s underlying software is now at version 3.2.1.
Apple has recently released iOS 4.0.1, a promised update tasked with replacing an algorithm that calculates how many signal bars are displayed on the phone’s screen, and iOS 3.2.1, an update for iPad owners that improves Wi-Fi connectivity, fixes an issue that could prevent copy and paste of single-page PDF attachments in Mail, addresses an issue that could cause video playback to freeze, improves reliability of video-out when using iPad Dock Connector to VGA Adapter, and adds Bing as an option for Safari's search field. To update their devices, Apple advises customers to use iTunes.
However, there are more IPSW download sources. Softpedia is one of them. iPhone and iPod touch users can use this here link to grab their respective software update for free, then use iTunes to selectively restore to it. Apple's download links for iOS 4.0.1 are also public (see below).
Another is the all-IPSW download source - felixbruns.de. This source also offers up IPSW downloads that were once paid for iPod touch owners.
The site owner features a short list of instructions on how to restore or update your iPod/iPhone/iPad. Felix Bruns explains: “After downloading the desired firmware below, you can shift-click (PC) or option-click (Mac) the Restore or Update buttons in iTunes. A file dialog will open and let you choose the downloaded ipsw-file.”
Should the browser used to download change the IPSW file into a zip-file, users can just rename it to end in .ipsw and iTunes will accept it, Bruns claims.
Update: article updated to remove some references to jailbreak / unlocking sites linked to by Felix Bruns.