I've got an application with about 35~ different settings in different categories.
What are the best practices to expose this to the client.
Secondly is there any VS.NET add-on or library (commercial or not) which can help to speed up this process. Something like "Property Grid" maybe but with a more professional and user friendly look.
All of the settings based on a class and couple of subclasses.
Have you looked at the design implemented by Visual Studio itself which is a tree view for the categories and a panel that updates when each category is selected?
I haven't been able to find any examples on Code Project (I'm probably searching for the wrong terms), but I have found this tutorial which walks you through three different visualisations. It's dated 2004 so there are probably newer pages out there, but it'll be a good starting point.