Google provides a way to check your account activity in GMail. Using this facility you can verify if some one else is also accessing your Gmail account. It is quite possible for someone to get your credentials particularly when you are using a shared public computers. To see your account activity, click the Details link next to the Last account activity line at the bottom of any Gmail page
The ‘Access type’ column to find out who 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.
Location (IP address)
In this column the last 10 IP addresses would be listed from where your mail was accessed from, and the associated locations.
If your mail is currently being accessed from another location, the ‘Concurrent session information’ would be shown in a table (as shown in the above image). If there are other sessions displayed, this could mean that you simply have another browser4 window open with Gmail loaded, or that you’re sign in on another computer. If you’re concerned about any concurrent access, you can sign out all sessions other than your current session by clicking Sign out all other sessions.
Unfortunately the Last Accessed information is not applicable for accessing any other Google services using your id and password. I tried logging in another machine to the accounts.google.com and navigated in the page, but GMail did not reported this activity. The feature is for “Account Activity” not just Gmail activity, so they should consider including other google services too for including in this report.