From cFos Software:
cFos Twitter Notifier is a program which runs in the background and periodically checks, whether new Twitter Statuses are available. If there is something new, it displays a notification icon in the windows taskbar and a balloon tip. If you click on the balloon or the taskbar icon, twitter.com is started so you can read the new statuses.
cFos Twitter Notifier uses OAuth. At first startup you need to authorize cFos Twitter Notifier to access your Twitter account. You don't have to give cFos Twitter Notifier your user name or password. When first started, Twitter asks you, if you allow cFos Twitter Notifier to access your account and gives you a PIN. You must enter this PIN into cFos Twitter Notifier's input box. cFos Twitter Notifier then gets an access token, which you can revoke at any time.