The Service Pack 1 for Visual Web Developer 200 Express was released sometime back by Microsoft. I upgraded my VWD 2008 to SP1. This now allows me to have multiple projects within the same solution. This feature was not present in any of the express editions and is a welcome addition.
Earlier if you wanted to build separate class library projects for Data Access and Business Logic, you could not do so in Express editions. What one had to do was to create different sub-folders within the App-Code directory and code the classes in these sub-folders. The problem with this was that if your application was big then compiling the whole thing took a lot of time. With different projects you can easily separate your classes which allows for fast compiling and easy debugging.
With SP1, the Entity Data Framework has also been added. I had seen a video on Entity Framework at asp.net and this was something which I would love to explore.
There must be other feature enhancements, which I haven't looked at right now. But if you haven't upgraded to SP1, I suggest you do so!