You're probably aware that using dumpbin.exe is very useful if you need to P/Invoke.  dumpbinGUI.exe is a tool that I've been using for years that you might be interested in.  It adds a simply context menu to the Windows shell, so you can right click any DLL or LIB and view it's exports (among other things).

The install leaves a bit to be desired.  You have to have a dev tool installed, and you must modify your path to allow dumpbinGUI to find a couple files.  If you have Studio 2003 installed in the default location, add these to your system path:

C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\bin
C:\Program Files\Microsoft Visual Studio .NET 2003\Common7\IDE