Apple has released its iCloud website (http://www.icloud.com/) as a beta and only for its developers. iCloud is the upcoming cloud service from Apple that replaces MobileMe. It includes the MobileMe staple such as Mail, Contacts, Calendar, Find My iPhone apps rewritten for iCloud. Apple also released iWorks for iOS beta which is iCloud enabled.
iCloud is meant for more than just Apple apps, as there are API to allow developers to take advantage of its sync and storage features. When apps are iCloud enabled, the data can be synced across iOS and Mac desktop with iCloud. For example you can access the same contacts and calendar on your iPhone, iPad, Mac and on the web using iCloud.com website.
iCloud requires iOS 5 and is expected to release together with iOS 5. On the desktop, iCloud requires Mac OS X Lion 10.7.2 which is expected around the release of iOS 5.
In addition to the beta, Apple has announced the pricing detail for additional iCloud storage. The first 5GB is free, and your purchased music, apps, books and Photo Stream do not count against this free storage. If you need more storage, its $20/year for additional 10GB, $40/year for additional 20GB and $100/year for additional 50GB.