A Chinese developer by the name of Chompers has released an alpha build of Android running on the HP Touchpad. Although it does not run extremely smoothly, it is undeniably an impressive feat. The .ipk has been made available for this preliminary build of Android, but is not rooted and has no Market.
This will not be your daily driver, but may be something users would like to play with before the official releases from CyanogenMod and other groups come out.
Download Link [Hosted on Chinese site, click the smaller button on the right of the blue button to download]