Apache OpenOffice Community Forum

Does anyone know of a good, stable open source PIM program, something like ACT! or Goldmine?

You can get the latest Evolution for Windows here:
http://download.go-oo.org/evo/
But I honestly have no idea if it has become more stable yet or not, I haven't tried it for a few years now.

You also have kde pim (part of kde project). For the windows port, you can start here
http://techbase.kde.org/Projects/KDE_on_Windows
No idea about the windows port, but on Linux it works wonderfully!