On CodePlex there is a new project at http://nsession.codeplex.com for sharing session state between classic ASP and ASP.NET
"The objective of this project is to allow ASP Classic to access ASP.NET out-of-process session stores in the same way that ASP.NET accesses them, and thus share the session state with ASP.NET.
In the initial release, we only support the ASP.NET state server as it is a popular choice and it offers better performance than the SQL Server session store. Please see the Documentation for further details."