Trying to open Gmail will currently result in a "502 Server Error: The server encountered a temporary error and could not complete your request." Other Google services, such as Search, Reader, etc., are working fine.
There's no official word from Google about the outage yet. As always, I feel uneasy; I rely on Gmail, and any prolonged outage is affecting my work and making me think about Google not being as bulletproof as most people usually think it is.
*Update: Google has posted a short note about the outage on their support page:
"We're aware of a problem with Gmail affecting a number of users. This problem occurred at approximately 1:30AM Pacific Time. We're working hard to resolve this problem and will post updates as we have them. We apologize for any inconvenience that this has caused."