Earlier today a beta version of iCloud.com accidentally leaked 2 new web apps, Notes and Reminders, presumably coming to iCloud web-portal. These apps make perfect sense to be on iCloud.com, as they already sync over iCloud across iPhone, iPod touch, and iPad devices, and Apple has added them as apps to the upcoming OS X 10.8 Mountain Lion.
The Reminders and Notes web apps weren't functional, nor was the login, and Apple quickly pulled the developer site offline. In other words, we weren't supposed to see this yet.
If we were to guess, WWDC 2012 would be the logical place for Apple to debut new iCloud features. That's where Steve Jobs debuted iCloud itself last year, and now more than ever the WWDC keynote is Apple's biggest software and services stage.
That's when it will start to become really interesting.
Source: Steve Troughton-Smith