Update: And it's back. According to Apple, the outage was resolved just before 4:00 p.m. EDT.
Original story: A number of iCloud services are down for some users. The disruption, which render services unavailable for some, has been taking place since about 11:30 a.m. EDT. Affected services include iCloud Backup, Drive, Documents in the Cloud, iMessage, Mail Drop, iWork for iCloud beta, and Photos.
Apple has acknowledged the outage on their System Status page. While service might not be out for everyone, Apple notes that users may experience slower than normal response from these services.
We'll let you know when everything is back to normal.