A great new MOSS resource from Microsoft which contains all the SDK's, web casts and other documents in one easy to access portal:

http://msdn.microsoft.com/moss

The link comes courtesy of a colleagues post on Thursday:

Eric Charran's WebLog

Anyone developing on MOSS or WSS v3 is aware of how frustrating the useless error messages received in the interface can be ("Unknown Error Occurred"), and often these are not at all accompanied by a message in the ULS logs.

I was having a terrible time with a new master page I was deploying, and finally realized something that should have been very obvious, but in case you missed it too, here is how you enable more detailed error messages for your portal:

1. Open up your sites web.config, and make the standard custom errors edit. You want it to be < customerrors mode="Off"/>
2. Then, something a bit less obvious, search for the CallStack="False" and change it to CallStack="True", you should find this in the "<safemode>" node.