This is an update to the ejectAllVolumes Dashboard Widget.
This version Will give you a list of mounted volumes. You can deselect any volumes that are listed to exclude them from the unmount action.
Links after the break.
Download
from me: ejectAllVolumes widget 1.1.0 (Zip file)
from Apple: ejectAllVolumes widget 1.1.0
For more details check out the ejectAllVolumes project page.