IIS 5.x and ASP.NET 3.5? Yes.
Database layer things: Avoid LINQ-to-SQL, it's deprectated. Your mainstream options will be Entity Framework and NHibernate. My choice is the second one.
LINQ is a query language for collection-based sources and it's used in a lot of scenarios. You need to think about it as a language feature instead of a database access technology - that statement is wrong! -.
Both Entity Framework and NHibernate have LINQ providers, meaning you can query databases with C# and their engine will translate LINQ to Entity Query Language or Hibernate Query Language, respectivelly.
Using LINQ providers or raw ADO.NET, or another OR/M approach would be just an opinion based on experience and personal points of view.
My point of view is any modern application should have database abstraction like an OR/M.
You can try a document database too, which is capable of storing native .NET objects, like RavenDB:
Using Entity Framework or NHiberante in your project would be a subjective decision because it seems your requirements are limited and both products are great monsters. And RavenDB is just a NoSQL database, and maybe could be more suitable for your needs and you can boost your productivity.
I don't know which are your exact requirements, sorry.