HOW TO: Run Scheduled Jobs in ASP.NET
Solution
Simulate a Windows Service using ASP.NET to run scheduled jobs
by Omar Al Zabir (CodeProject) - uses ASP.NET cache expiry to simulate a timer; works in shared hosting scenarios.
Combine Web and Windows Services to Run Your ASP.NET Code at Scheduled Intervals
by Andrew Needleman (MSDN Magazine) - shows how to create a custom Windows service to act as the scheduler and using web service to expose functionality.
Schedule a task to call a webpage using Task scheduler
by Steve Schofield - shows how to schedule a task to run in IIS using Windows Task Scheduler.
Related Resources
Microsoft TechNet: How To Schedule Tasks in Windows XP
MSDN: Using the Task Scheduler