In most of the airline web sites, there will be Flight Status Notification feature that you may sign up for when you want to be notified of a flight's status.  You can receive a text or a voice message with information updates on your flight or a flight you expect someone on.  You can choose to receive a voice message to your phone, a text message to a cell phone, alphanumeric pager, Personal Digital Assistant (PDA) or regular email account.

Another example can be job web sites, which usually will have job alerts feature in which job seekers will register for the particular key skill sets, experience, job category or location to receive job alerts on their e-mail accounts or mobile phones.  Whenever there are any job postings on the website specific to the registered job seeker's skill sets, experience, job category or location, an e-mail or SMS messages will be sent to the job seekers.

In the above example we can relate the job alert feature as Publisher and the job seekers as Subscribers.