At the end of June I run workshops with 2 ISVs both looking to completely re-develop their applications. One is entirely VB6, the other a combination of VB6 with C++.

The beauty of "starting from scratch" with a one to two year development plan is you can take a hard look at the latest technologies from Microsoft - and there are a lot of them! As a result, both application architectures at a high level ended up looking pretty similar.

The following links should help those teams drill in further - and maybe you?

In both cases we went with .NET Framework 3.5 SP1 as our base level technology (NB: SP1 is really a feature pack)

Presentation Tier

• Rich Client for power/frequent users, typically inside the firewall with the need to be occasionally connected
  • Windows Presentation Foundation 3.5 
    • In June we released the Composite Application Block for WPF
  • ADO.NET Synchronisation Services to a local database cache
  • Workflow Foundation for ....errr...workflow :-)
  • Communication to middle tier via HTTP/REST
• Browser Client for occasional users, typically outside the firewall
  • Silverlight 2.0
  • ASP.NET AJAX
  • Workflow Foundation

Middle Tier

• Serving both types of clients. Ability to scale out.
  • ADO.NET Data Services - exposing entities and operations
    • SP1 Documentation for Data Services
  • ADO.NET Entity Framework and LINQ to Entities - delivering object relational mapping
    • SP1 Documentation for Entity Framework
  • Workflow Foundation
  • Windows Communication Foundation to drive and respond to external systems
• Note: We ruled out LINQ to SQL in favour of LINQ to Entities - however worth saying that in both cases we only needed to support SQL Server and therefore LINQ to SQL would be a valid alternative
  • LINQ to SQL has shipped and N-tier development with it is nicely covered in the documentation and in Beths posts
    • Middle Tier
    • Presentation Tier
    • Data Tier

Data Tier

• Where we store all the data :-)
  • SQL Server 2008
    • Extended via SPs, Triggers and Types using TSQL or CLR integration as appropriate

Blogs (sample of the best):

• ADO.NET Team on Entity Framework http://blogs.msdn.com/adonet/archive/tags/Entity+Framework/default.aspx
• ADO.NET Data Services Team http://blogs.msdn.com/astoriateam/
• Sync Framework team http://blogs.msdn.com/sync/default.aspx 
• UK based Mike Taulty with some great content on ADO.NET Data Services, Entity Framework and Silverlight
• Tim Sneath (ex UK) on all things WPF/Silverlight http://blogs.msdn.com/tims 
• Product group WPF site http://windowsclient.net/
• Related - SQL Server Data Services http://blogs.msdn.com/ssds/default.aspx 

P.S. Both teams will be using Visual Basic 2008 :-) I thought you would like that one...