And Web Monitor also notifies you again once the site comes back up, so that you can relax and back off from full panic mode at 3am in the morning.

Web Monitor runs either as a desktop application, taskbar item or as a Windows Service and allows you to monitor up to 100 sites per instance. The Service Version also provides a remote Web interface to administer the Web Monitor Service over the Web (requires Internet Information Services and ASP.NET 2.0).

West Wind Web Monitor Features:
Web Site Monitoring
Monitor any number of Web sites simultaneously
Monitor HTTP result for a specific string contained in result
Search for result text or missing result text with plain text or RegEx expressions
Configure each site individually including messages, actions and check frequency
Recheck sites before failing to avoid false positives
Send POST data to the server if needed
Support for HTTP Authentication and SSL
Monitor sites once every few seconds or once a day - it's up to you
Hit maintenance links at regular intervals to perform automated Web tasks

Failure Notification and Recovery Processing
Send email in response to failures
Unlimited number of recipients are supported.
Execute one or two Web Links or Executables in response to a failure.
Detects site reactivation and send notification of reactivation.
Full Add-In model using any .NET language allows customization
of the entire process, including HTTP access, searching content,
emailing, logging and execution of executables.

Administration
Logging of failure and restart events
Log files store data in XML format for external Log parsing
Four operational modes:
Desktop Operation
Task Tray Operation
Windows Service Operation (Service Version)
ASP.NET Web Front end to administer Web Monitor remotely

Extensibility
Add-in support lets you extend Web Monitor with any .NET Language
Customizable and pluggable .NET C# source code version available
to plug Web Monitor functionality into your own .NET applications.