A while ago I was looking for an alternative to System.Diagnostics.Trace and found Log4Net. I know the patterns and practices group have created enterprise logging but I find Log4Net nice and easy to use. I created some documentation and samples on my website at http://www.recneps.co.uk/log4net.aspx.
The BlackMarble.Diagnostics.Logging libraries encapulate both System.Diagnostic.Trace and Log4Net so that we can use a standard way of logging and then configure at runtime one we want to use.