My DAL and BLL are going to be used as base classes for Webforms that are similar. However, I want these base classes to be "hidden" away and just inherited from. If there needs to be a change it's done from one place and the dlls (or other solution) is just redistributed. I know you can do such a thing with DLLs, but I was wondering if .NET 3.5 has other ways of doing the same thing.
not really. Are you looking for more efficiency? ease of use? Distributing DLLs is going to be a good way of keeping your code separate while allowing them to include it in an application and use it as a base class. .NET calls them "assemblies" but it's really just another DLL users can include.