Error logging for asp.net

See http://code.google.com/p/elmah/

ELMAH (Error Logging Modules and Handlers) is an application-wide error logging facility that is completely pluggable. It can be
dynamically added to a running ASP.NET web application, or even all ASP.NET web applications on a machine, without any need for
re-compilation or re-deployment.
Once ELMAH has been dropped into a running web application and configured appropriately, you get the following facilities without
changing a single line of your code:

.Logging of nearly all unhandled exceptions.

.A web page to remotely view the entire log of recoded exceptions.

.A web page to remotely view the full details of any one logged exception.

.In many cases, you can review the original yellow screen of death that ASP.NET generated for a given exception, even with
customErrors mode turned off.

.An e-mail notification of each error at the time it occurs.

.An RSS feed of the last 15 errors from the log.