A few days ago, I published my second HOWTO dedicated to Quantum GIS developers using Visual C++ under Windows. The whole series is devoted to using Visual C++ 2005 compiler to build QT library and to start QGIS development on Widows.
The process is more complex than building QT library but it’s doable. I tried to do my best to give good explanation of every detail and requirement. There is also provided complete Visual C++ 2005 solution with subprojects. So, you can just open if with Visual C++ 2005 and start QGIS development. Almost. The only thing that requires manual work is preparation of the environment: directories structure for compilation output, installation of dependencies like GDAL, GEOS and SQLite 3 libraries. (Here you can find some helpful resources for GEOS related to building with Visual C++ 2005). You can install GDAL and sqlite from FWTools package (big thanks to Frank Warmerdam). But remember, you will need to build GEOS yourself, because the binary that comes with FWTools provides C API but QGIS uses C++ API of GEOS. Don’t worry, it’s quite simple, just 5 steps.
If you will have any comments, questions or problems, don’t hesitate to contact me. You can catch me also on the QGIS IRC channel - #qgis. This channel is available on the irc.freenode.net server. My IRC nick is mloskot.