This seems to be a bummer. Color coding and intellisense for VBScript code in Classic ASP pages have been deprecated in VS 2008.
There is a workaround for making it work for files with the .vbs extension but no solution for .asp pages. Hopefully someone would come up with a hack to get it working again.
Until then Microsoft's answer is for us to use VS 2005 or Visual Web Developer 2005. But don't install VWD if you already have VS 2008 installed since VWD will take over all file associations leaving 2008 broken.
You can let Microsoft know how much this sucks by ranting here: http://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=290845