<p>This question is similar to my  earlier question.</p>

<p>I have used ASP .Net in Visual Studio 2005 about 4 years ago. How long would it take to get back up to speed with the latest versions?</p>

Not very long. The major addition to VS 2008 is support for Linq, but you don't have to use this (or any of the new features).
The IDE is extremely similar to VS 2005.
Essentially, 2005 targets the 3.0 framework, and 2008 target the 3.5 framework, but these are both just expansions of the 2.0 framework, and not new versions (unlike the change from 1.1 to 2.0).