<p>I am having severe performance issues when compiling a moderately large ASP.Net website in Visual Studio 2008 (targeting .Net 3.5). I know there are some tips &amp; registry hacks for improving compilation performance in VS 2005, are there any for VS 2008? Specifically, it seems that VS 2008 is compiling the whole website every time F5 is hit, even when no files have changed in that project since the last compile, or perhaps there is some way to skip the validation stage? </p>

I'm guessing this is an ASP.Net Website project and
not
an ASP.Net Web Application project. You'll get better compile performance from a Web Application project so you might consider converting it.
For a Website project, you can open the Website in Visual Studio, right click the web site project node in the Solution Explorer and click Properties. When the dialog box opens, click the Build item and set the item labeled "Before Running Startup Page" to "No Build" or "Build Page". This will prevent Visual Studio from compiling all the pages in your site and improve your local development experience at the cost of reduced compilation. Probably a worthy trade-off in your case.