I've converted my old Space Hogs game project to XNA 4.0 (it was originally written in XNA 1.0). There were enough API changes to make it a pain, but I think I have everything working now.
This game was developed by myself, Jason Kim, Joseph Ahn, Vjekoslav Kovacevic, and Daniel Guinn for a computer animation class during Winter Quarter 2007.
You can find a zip file here. This requires XNA 4.0 and the February 2010 DX packages to be installed on your machine. For convenience, I've included both of the redistributable packages in the zip file.
The source can be found on BitBucket.