Today is the big day when the millions of owners of iOS devices get to update to the latest and greatest version of Apple’s mobile operating system, the iOS 5. If history is anything to go by, the iOS 5 update should appear in iTunes around 10 a.m. Pacific Time, as did the iOS 3 and 4 firmware updates. Laying the groundwork for the much-anticipated software update, the company yesterday issued iTunes 10.5, the App Store published a bunch of iOS 5 app updates while digital magazines began populating the Newsstand app.

iCloud, Apple’s free of charge online services suite to go along with iOS 5, has gone live for the general public, too. You can sign up for iCloud at icloud.com using your Apple ID credentials (check out the subtle iCloud logo animation when opening the site, very nice). iCloud gives you five gigabytes of free storage (paid upgrades are available), but content purchases on the iTunes Store don’t count against your quota. As you know, an Apple ID is a user name you can use for just about everything you do with Apple, which includes shopping the iTunes Store, logging in to iChat or MobileMe, buying products from the Apple Online Store and now it lets you access iCloud to store your content.

The iCloud registration process requires you to select your language and time zone. The prettified web interface looks business and is consistent with the linen theme in OS X Lion and the iOS 5 device setup interface, ensuring no customer is left confused and underscoring how iOS 5 and iCloud are meant to work together. The interface includes web apps to access, review and edit your contacts, calendars and email. You can also locate your device on a map using the Find My iPhone web app which works in conjunction with a free iOS app from the App Store. You will also be able to see your friends who have opted to share their location with you, which requires the free Find My Friends app for iOS, not available yet at post time. The iCloud interface also includes the web-based version of iWork productivity suite, allowing you to view and share your office documents (but not edit them in the cloud)