Of course new .NET Framework 4.0 has features that could be used by developers mostly.
In general for business .NET 4.0 Framework main focus is on performance and security improvement.
There are some features that could be useful for end users, development enterprise and business application, business application design and architecture.

– Memory-Mapped Files.
The .NET Framework now supports memory-mapped files. Developers can use memory-mapped files to edit very large files and to create shared memory for interprocess communication.

– 64-Bit Operating Systems and Processes.
Developers can identify 64-bit operating systems and processes. This will increase performance of both server and desktop side application.

– Client Profile.
Main features is integration with MS Office applications. All Office 2007 and Office 2010 project templates.

– Integrated Windows Authentication.
A lot of existing troubles with authentication could be solver.

– Networking performance.
Support for Network Address Translation (NAT) traversal using IPv6 and Teredo.

– Windows Workflow Foundation
This tools could be used for UML modeling. It could help software architects to design business architecture and describe business logic.
The main feature is Workflow Activity Model also known as ‘Activity diagram’ with rich composite activity options and Built-In Activity Library.

For detailed information you could visit official websites of the .NET 4.0 Framework’s parts:

ASP.NET

Silverlight

Common Language Runtime (CLR)

Dynamic Language Runtime (DLR)

.NET Compact Framework

.NET Micro Framework

Windows Presentation Foundation (WPF)

Windows Communication Foundation (WCF)

Windows Workflow Foundation (WF)

ADO.NET

ADO.NET Entity Framework

ADO.NET Data Services