If you are a Gmail, or Google Apps for Business or Education user, you likely noticed a problems accessing your email accounts starting at around 11:00 AM Pacific time. It should be back up by the time you find yourself reading this.
During the downtime, access to Gmail from mobile devices, via the web, and Google Apps Sync would have been down. This also would have affected access to contacts, Google Voice and Google Talk, and features of the Google Apps Dashboard.
Fortunately, Google’s response to this was swift, and everything was restored quickly – just a 30-40 minute downtime for most people.
If you’re still having problems, they are likely unrelated to the downtime itself, and you should seek technical support.