How can I extract all classes into separate file?

For those that are running a newer version of Visual Studio, there is yet another solution (I realize the question mentions VS 2008). Visual Studio 2017 offers functionality similar to what Eduardo Molteni described for CodeRush. You simply click on a class name, click on the light bulb icon to the left, and select "Move type to xxxx.cs".

If you're using ReSharper 5, on the solution explorer, press Ctrl+Shift+R to invoke the Refactor menu (or alternatively right-click and locate it) and select "Move Types into Matching Files"