Google Account is one important account with which all the google services are linked like gmail, blogger, picasa, buzz, calendar etc. Just in case if you see some suspicious activity happening across your account at any of google services you are using, you can revoke access from these apps or web services using your google account.
Follow the procedure below to do the same.
Stop Apps Using Your Google Account
1. Go to this page, you will need to login with google account for the page to open.
2. Once the page is opened you will see list of web services and apps for which you have grated access to use your google account as shown in the image below.
3. For all those applications you are not sure, you can click the link Revoke Access to stop or prevent that application using your google account in future.