Gmail adding log-in monitoring features
Wondering if you're Gmail account is open in multiple locations? Just look at the very, very bottom of the main Gmail page. It'll say something to the sound of: "This account is open in one other location." Click on the "details" link next to it to get taken to, well, a details page.
It'll give you the deets on the most recent sessions including the access type and IP address. It's not the end-all for email hijacking, but at the very least it'll help you point-out intruders. And if you don't see the feature yet, sit tight, Google is slowly rolling out the feature to all accounts.