After a couple weeks of hard work, Marcelo (aka setanta) has successfully set up a VMWare Appliance for Maemo SDK. It's based on Xubuntu 7.04 and ships only the Maemo 3.1 (bora) targets. Gregale version (2.2) was not included in order to save some disk space.
Marcelo has also submitted a project in maemo garage. While it is not approved, you can download it from here.
Update: The project has been approved in maemo garage. Go for it!