Web

• ChangeDetection.com - simple easy-to-use website that sends you an e-mail alert when a webpage you specify changes.  You can specify several options, like words to look for in the change that occurs.
• Mon.itor.us - site monitoring service with a very slick AJAX interface.  They can send you an e-mail if and when your site goes down and when it comes back up.
• Yahoo! PIPES - cool service from Yahoo! (also with a very slick user interface) that allows you to manipulate data from various sources in various ways.  One simple PIPE I created in a matter of minutes was to filter out entries from an RSS feed containing certain words.  It was as simple as: