Apple today published a new version of its iCloud status page, on which all of the various services and features of iCloud are listed individually. This new status page lets you see at a glance if there are any problems with iCloud, instead of leaving you frustrated, wondering why your iCloud mail isn't working. You may still be frustrated when you learn that the service is down, but at least you'll know why something isn't working.
Besides showing current status, the page also has a timeline that displays the status from the last few days.
If you use iCloud, I recommend adding the Apple Services, Stores, and iCloud status page to your browser bookmarks.