When I open a Visual Studio command prompt (for example, opened with menu Start -> Programs -> Microsoft Visual Studio 2008 -> Visual Studio Tools -> Visual Studio 2008 Command Prompt), I get:
Setting environment for using Microsoft Visual Studio 2008 x86 tools.
C:\Program Files\Microsoft Visual Studio 9.0\Common7\IDE>
What kind of tools are available, and what are the most common uses of this command prompt?
It basically just sets several of the Visual Studio binary locations into the PATH
environment variable for that command window instance. This means you can use all the various commands and tools without having to include the full paths.
There's a partial list of some of the tools available on MSDN in .NET Framework Tools and Tools (.NET Framework).