<p>How do you extract an RT_RCDATA section from a Win32 executable (preferably in C#)?</p>
<p>The only way I know how to do this currently is opening up the EXE in Visual Studio.  I'd love to be able to do this entirely in C# if possible.</p>
<p>Thanks!</p>

P/Invoke LoadResource will be your safest bet.
Otherwise you'll have to write your own
P/E
processor eg.
PE Processor example
.  The processor isn't the end of the world, but as you can see much more involved than a P/Invoke.
Almost forgot,as far as tools go, most P/E browsers will do this for you.  Eg. P/E Explorer, which is available but not really being developed.  I've also used IDA Pro for stuff like this.  A quick IDA plugin would do this easily.