My first post, here's a recommendation:
Go and download the .Net 2.0 version of ELMAH.
Very easy and quick to include in your projects, and very useful!
The GotDotNet project for ELMAH is here
Oh, yeah, ELMAH stands for “Error Logging Modules and Handlers”
Update: since GotDotNet was phased out, the project moved to http://www.elmah.org/