UPDATE: Gmail is back up for, however Google continues to investigate the issue.
Gmail service has been down for some users Tuesday afternoon. Google states that they are “continuing to investigate this issue” and will provide an update by 2:16 PM PDT today. This issue appears to be affecting users who access Gmail via the web interface as well as mobile applications such as the Gmail App for BlackBerry.
Gmail can be access via IMAP or POP. You can find instructions for how to do this here.