The links provided by Naerling and Mark is well worth a look, and I hope you'll find the following useful too.
Rémy Fannader has created a very nice web
Caminao's Ways[
^] that I hope you'll find interesting.
The
Data Model Resource Book series[
^] is also something that I'll recommend.
The links above provides valuable information about how to structure your enterprise application designs, but does not touch on .Net or c#.
Inside Windows Communication Foundation[
^] provides a good introduction to WCF, and you should probably know about
Nicholas Allen's Blog[
^] too.
Best regards
Espen Harlinn