Hello,
Thanks for your interest in our ASP.NET product line.
Visual Studio version is typically tied against .NET framework version. They typically go like that
ASP.NET 1.x - VS 2003
ASP.NET 2.x - VS 2005
ASP.NET 3.x - VS 2008
Of course, this is just the general guideline, there are exceptions to this rule (e.g. VS 2008 supports .NET 3.x and 2.x, you can set this up in Options).
In any case, here is the ASP.NET suite download link:
http://www.infragistics.com/dotnet/netadvantage/aspnet.aspx#Downloads
And download the following version of NetAdvantage for ASP.NET (click the download link on the right)
NetAdvantage for ASP.NET 2008 Vol. 2 [CLR 2.X]
If you have any issues, just let us know.