Depends on how much experience you carry and what have you worked and learn't previously.
Basics: Knowledge of GAC and assemblies, plus http-handlers on IIS side
C#: Concept of Delegates and Generics should always be clear and try using as-many demo examples of same.
ASP.Net: General 2.0 features like Master-Pages, Themes and Site-Navigation
There is much to learn depending on what you are going to end-up working on.
They will be used by more and more developers and will become the standard for the next thousand years; or not! I don't think there are many people who can tell the future. However, if you want to know about the present, then look at some of the products that are on the market that make use of these technologies, and the books written about them.
It's impossible to tell you which ones to learn, since we don't know what you are aiming for or what are the requirements in your area. Take a look around at the sort of jobs you are interested in, or the ones being advertised and try to decide based on where the opportunities exist in the market that you are trying to break into.