Here's something for you girls: Gmail -- Last account activity

What is 'Last account activity'?
Last account activity shows you information about recent activity in your mail. Recent activity includes any time that your mail was accessed using a regular web browser, a POP1 client, a mobile device, etc. We'll list the IP address that accessed your mail, the associated location, as well as the time and date.
To see your account activity, click the Details link next to the Last account activity line at the bottom of any Gmail page.

If you're concerned about unauthorized access to your mail, you'll be able to use the data in the 'Access type' column to find out if and when someone accessed your mail. For instance, if the column shows any POP access, but you don't use POP to collect your mail, it may be a sign that your account has been compromised.

http://mail.google.com/support/bin/answer.py?ctx=%67mail&answer=45938