I can't figure this one out. I can download a win32 binary of flex 2.5.4a from gnuwin32, but I'd like to build the latest version (2.5.35) using Visual Studio 2005. I suppose I could build in in cygwin, but where is the fun in that?
Note that Flex is seriously out-of-date on Windows when it comes to generating C++ scanners. Recent Flex versions which are able to generate ISO C++ scanners do not support Win32 (MinGW or VS), so you're probably better of trying to generate a C scanner and call it from C++.
since nobody provided a satisfactory answer to my question, i am posting my final solution here.
i was unable to find a way to build flex in vs 2005 or vs 2008. instead, i am using the flex that is distributed with cygwin, which is pretty recent. in order to save myself the hassle of installing cygwin on every machine that i need to use flex on, i just saved off the dependencies: cygwin1.dll and cygintl-8.dll.
there is only one caveat - cygwin's flex also depends on m4, though you won't see it on the dependency walker. it needs to be in the path, which makes it a pain. you can use cygwin's m4.exe, but it depends on cygwin1.dll also, which will need to be in the path for m4 to execute.
even so, i just check all of those files into my svn under a tools folder and then whenever i need to develop on another machine, get my code and flex with svn, copy m4.exe and cygwin1.dll to the windows\system32 folder, and i'm in business.
You can also download the MINGW (Minimalist GNU for Windows) build of flex 2.5.35 at sourceforge.net. This build may not be entirely self-contained; the release notes suggest that certain components of MSYS (Minimal SYSytem) are required.