EDIT 6/31/2010: This works just the same for VS2010. The second paragraph below made me smile... I did the same thing when 2010 came out - Steve
You probably should not upgrade any VS Tools project from Visual Studio 2005 to 2008 because - although it works - there are several things that don't work... or are hard to do.
But... that's not me. I loaded 2008 the day it came out.
If you upgrade, you'll have to copy the DynamicsGPProject.zip file (just search for it) into C:\Documents and Settings\username\My Documents\Visual Studio 2008\Templates\ProjectTemplates\Visual Basic. That will allow you to create a VS Tools project.
Here's how to move the 'Item Template' for the Dynamics GP form, so you can create forms directly in VS 2008:
Copy C:\Program Files\Microsoft Visual Studio 8\Common7\IDE\ItemTemplates\VisualBasic\1033\DynamicsGPform.zip
to
C:\Documents and Settings\sgray\My Documents\Visual Studio 2008\Templates\ItemTemplates\Visual Basic
It'll appear below the standard templates in the 'my templates' area
My thanks to Patrick on the Dynamics GP support team, they've always been very good.