Last month I blogged a about the way Wubi filesystems are organised via a FUSE mounted ntfs-3g loop back mounted file system. This blog article has been getting quite a few hits, so I thought some extra Wubi links may be helpful.
1. Wubi is a way to allow Windows users to install (and uninstall) Ubuntu as if it's a Windows application in a simple straight forward way that does not modify the Windows partitioning.
2. The official Wubi Wiki page contains all you need to know to get started on Wubi.
3. Bugs can be reported and tracked on the Wubi LaunchPad project page.
4. The Wubi project page can be found here.
5. The Wubi Blogosphere may have some useful tips and hints about Wubi.
6. Some extra historical context to this project can be found at Wikipedia.
7. A video of Agostino Russo's Wubi talk at UDS Prague (Intrepid Ibex) is worth watching; the talk also contains a demo of the Wubi installer.
Hope that's a helpful start.