Right Web Monitor (commercial license) at $149
Right, Web Monitor is a handy tool for detecting changes in web resources (web pages, files, etc). It constantly monitors specified resources and notifies you when a change occurs. The program features the ability to check a certain part of a monitored resource and includes a comprehensive notification system (pop-up windows, sound, e-mail), proxy server support, and multithreaded data transfer. Can download changed files and check mailboxes.