We recently announced that we have discontinued development of Expression Web, Expression Design, and Expression Encoder, and that Blend will be included as a standalone product with Visual Studio. You can read the full announcement on our community page at http://msdn.microsoft.com/expression.
The Expression Gallery is now closed and the project files are no longer available. The owners of projects in the Gallery were notified of the closure in advance, and were invited to submit items to the MSDN Gallery or Visual Studio Gallery.
Some popular Expression Gallery projects were migrated and are available at the links listed below.
If you are looking for another project that was in the Expression Gallery, you can search the MSDN Gallery, the Visual Studio Gallery, and the Archive Gallery to see whether the project owner migrated the project.