Currently the .NET 3.0 Framework is in Visual Studio 2008 (Codename: Orcas) and also supports the .NET 3.5 framework which is in Beta 2. (VS2K8 is also still in Beta)
MS has released a few plugins for VS2K5 that will allow you to work with the .NET 3.x framework (for example, a plugin to create WPF applications) so you do have that option.
The new release of the framework has lots of "cool" new features, for example:
Windows Presentation Foundation (WPF)
Language Integrated Query (LINQ)
Windows Communcation Foundation (WCF)
Google searches will net you vast amounts of information on any one of those items above.
Read this if you want to know how to get a correct reply for your question:
Technical Editor for:
Beginning Visual C# 2008
Professional Search Engine Optimization with ASP.NET
Professional IIS 7 and ASP.NET Integrated Programming
Wrox Blox: Introduction to Google Gears
Wrox Blox: Create Amazing Custom User Interfaces with WPF and .NET 3.0