When looking inside of your Google Apps “Organization & users” tab under the administrative control panel, you can see the last time that someone has logged in when you look at the last column to the left of the user listing for your domain.
However, that statistic can often be misleading: due to cached sign-in capabilities in modern browsers, a user could potentially stay signed in for days. This can be misrepresented in terms of whether a user is actually using Google Apps at a given time or not, and can often be a great troubleshooting step when someone is experiencing user-specific technical problems. Here is how you can force a sign out and subsequently an entirely new log in session, no matter where the user may have their credentials cached from possible logging in at multiple locations.
From the “Organization & users” tab in your administrative console, go ahead and click on the user you would like to sign out.
Upon entering into a user’s account information, you’ll see the ability to reset sign-in cookies under the password reset section.
Being able to see this requires you to be an administrator and for the user in question to be a regular user. For example, an administrator is unable to see this functionality for another administrator.
Some of the issues that this may resolve include changes to domain-wide administrative sessions, problems accessing certain Google Apps services and not being able to see newly added Google Apps Marketplace apps prior to the previous sign-in. Much like rebooting a computer, signing out of Google Apps domain-wide is a great troubleshooting step when something is not working quite right.
Have you ever used your administrative privileges to sign a user out? Did you do it for troubleshooting purposes?