I’ve seen a growing number of free software Windows programs where the recommended (or only) build procedure is to cross-build from Linux. I really like this idea.
The latest I noticed that did this is the Clementine music player (which I’m rather excited about). This is a fork of amaroK, with the KDE parts stripped to make in plain Qt, and thus portable. Their web site is http://www.clementine-player.org/. Their Windows build directions are here, and involves a chroot on a Debian system. This, of course, lends itself to the idea of projects eventually distributing build VM appliances, or if LXC takes off, premade build containers.