For those building OpenOffice.org on Win32, it might be interesting that I've extended ccache to deal with MSVC. I've done it during our Novell HackWeek; I hope you'll enjoy the result as much as I enjoyed the hacking ;-)
It is easy to use, instead of guw.exe /path/to/cl.exe, you'll use guw.exe ccache.exe /path/to/cl.exe in your CXX environment variable after having sourced the environment. To see the ccache statistic, use ccache -s. You can override the directory where is the cache stored by exporting CCACHE_DIR="c:\where\you\want". Should you find any bugs, please send me patches :-)
I've not measured the speedup too much yet, but it was >20% in vcl compared to non-ccache run, the penalty of the initial fill of the cache was like 17% [compared to non-ccache]. Would be great if someone did a measurement of the entire build.