The removal of the extra volumes from the sidebars is trivial: just right-click (or Control+click) on the drive entry and select the Remove from Sidebar option.
But how to deal with the icons on the desktop? One possibility is to open the Finder's preferences and tell it to not show entries for hard disks. The downside is that all direct accesses to the file system will disappear, including those that represent external disks.
A slightly better solution is to mark the volume's mount point as hidden, which will effectively make it invisible to the Finder. To do this you have to set the invisible extended attribute on the folder by using the SetFile(1) utility (stored in /Developer/Tools, thus included in Xcode). For example, to hide our example /Users mount point:
# /Developer/Tools/SetFile -a V /UsersYou'll need to relaunch the Finder for the changes to take effect.
The above is not perfect, though: the mount point will be hidden from all Finder windows, not only from the desktop. I don't know if there is any better way to achieve this, but this one does the trick...