Minimizing build times for C++ projects under VS2005 and later

I recently looked over our build times in our now quite large C++ project. They have slowly been creeping towards the unacceptable, but after some tweeking they are now about a third of what they were. Just wanted to list what I did here. Some things are specific for Visual Studio (we're using 2005) but most will work on any IDE.

• Use precompiled header. I think precompiled headers have an undeserved bad reputation. If they are used correctly they can reduce your compile time tremendously, especially if you use template libraries to any extent (like STL and boost). Any big, static header file should go with the precompiled stuff (windows.h, winsock, and all stl/boost headers are obvious candidates). Check out this link on how to get it right.
• Minimize unnessecary includes. Our project was full of unnessesary includes in header files, mostly of the nature that they could be replaced with a forward declaration. Forward declaration really is your friend! However, you should never be tempted to violate the standard rule that "Every header file should be self-sufficient". That is, a header file should not be dependent of includes made by a header file which itself includes.
• Set the Debug Information Format to your needs. I usually use /Zi, which does not include information for Edit and Continue like the default setting. This actually makes a big difference in the size of the database files, and therefore reduces compile time. Of course, if you actually do frequently use Edit and Contiune, you should use the default.
• Define WIN32_LEAN_AND_MEAN. This strips away seldomly used parts of windows.h, which is a monster to compile (and should be placed with the precompiled headers). It is a small chance that you will actually need anything that this defines strips away.
• Use the /MP switch in Visual Studio. Actually, in VS2005 this is an undocumented switch that has to be added to the "Additional command line arguments" field under C++ settings. It lets the compiler use more than one core during compilation. Just activating this switch on my dual core machine reduced the total build time with about 30 %.
• Get yourself a SSD disk. This one speaks for itself. The problem is just to persuade your IT department that you need one.