So I have not embeded many reports in ASP.NET web sites to date so I am a little late on this news.  I finally added a report to a ASP.NET 3.5 web site and used the Report Viewer control.  After deploying the control I received this message:

Could not load file or assembly 'Microsoft.ReportViewer.WebForms, Version=9.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.

I read a few newsgroup postings about this which gave some hard to swallow advice.  I figured there must be a better way.  There is.

All you need to do is install the Redistributable package on the target web server for your version of report viewer.

For VS2008 use this one:
http://www.microsoft.com/downloads/details.aspx?FamilyID=CC96C246-61E5-4D9E-BB5F-416D75A1B9EF&displaylang=en

For VS2005 use this:
http://www.microsoft.com/downloads/details.aspx?FamilyId=35F23B3C-3B3F-4377-9AE1-26321F99FDF0&displaylang=en

Installing these and restarting IIS did the trick!

EDIT: Related to this is my other blog here: http://davidsandor.com/blogs/tipsandtricks/archive/2008/07/16/solved-the-base-class-includes-the-field-reportviewer1-but-its-type-microsoft-reporting-webforms-reportviewer-is-not-compatible-with-the-type-of-control-microsoft-reporting-webforms-reportviewer.aspx There are apparently issues when upgrading a Visual Studio 2005 project with a report viewer control to a Visual Studio 2008 project.  You must hack your .SLN or .CSPROJ files to fix the annoying bug.