.Net technologies blueprint: .NET frameworks & IDE
1.0 obsolete
1.1 VS 2003
* win 2003 has built in
2.0 (sp1) VS 2005/8/(?)10
3.0 WPF, WCF, WF, VS 2005/8/(?)10
3.5 (sp1) Linq, C#3.5, Entity fw..., sp1: System.Web.Abstraction, Sys.Web.Routing. VS 2008/(?)10
* win 2008 has built in
* the same runtime
* upgrade is convinient (not risky , backward compat)
4.0 VS 2010
* new machine.config, mscorlib, runtime
* C#4.0, ASP.NET 4.0
* upgrade might be risky, requeres changes in web.config.
mono
* integration with VS
* MonoDev
* The Mono API today is somewhere in between .NET 2.0 and .NET 3.5,
* cross platform
we recommend:
VS 2008/.NET 3.5
* C# 3.5
* all-in-one technologies.
* upgrade from .NET 2.0 does not require any code change
MONO for cross platform only.
VS 2010/.NET 4.0 - in the future.

Comments
Hi.
I want to add some words about IDE's.
VS 2010 is good tool to develop: comfortable code editor based on WPF(zoom in), new architecture features like generation sequence diagram, view call hierarchy and etc. Possible to work in parallel with VS2010 and previous VS - just save old solution file (depends on projects type - on class library, win service and console projects works proper).
SharpDevelop: easy, fast, grows quickly, supports most project types, open-source. Very suite for sources observing, less for "deep" development(currently).
Notepad++: very comfort to view single source files, supports highlighting of most languages and formats.
Regards, Michael
Good points, Michael.