There are two types of images available for N900. One that contains only open source software from MeeGo repositories and one that has some Nokia proprietary components installed.
The open image for N900 can be obtained from http://repo.meego.com/MeeGo/devel/n900/images/. There are four kind of files
The image with Nokia proprietary components can be loaded from here: http://repo.meego.com/MeeGo/releases/1.0/core/images/
Day one codedrop available here: http://tablets-dev.nokia.com/meego-codedrop.php
Note that you must own a N900 device and accept the Nokia End User License Agreement to access the files.
There are two kinds of files available
NOTE: You can use the kernel from the open image also with the closed image
The closed image contains the following proprietary components