Thanks to this awesome thread I now have a working SDK on my N900!

I did things a little differently though... I read about resizing partitions so I had already moved about 10GB from MyDocs to /home. Because of this I avoided the use of an image file and just started with the maemo rootstrap, which I extracted into /home/sdk. I had to modify qchroot and closechroot so they didn't try to mount/unmount the image. Tigerite's instructions for going from bare rootstrap to installed SDK worked a treat.

I'd like to make a little contribution, which is to explain the problem with Qt. If you've tried to use libqt4-dev you will have noticed that qmake doesn't work. Qt does not fit into the debian/scratchbox packaging style because it builds host tools and target tools at the same time. To prevent it from taking a million years to build the official packages under scratchbox, qmake (and the other "host" tools) are built for x86. Thus these packages only work properly on a x86-compatible machine.

To correct this, I have grabbed the sources used to build the libqt4-dev package and built the host tools using the native compiler. To use these, unpack this tarball into /usr (eg. cd /usr; tar zxf /path/to/qttools.tgz).

Happy Hacking!