Are there any way I can have a Dashboard Widget visible all the time on the desktop?
You can drag a widget outside the "screen" it appears in, if you enable the debugging mode for the Dashboard.


Open a Terminal window, and execute the following command: defaults write com.apple.dashboard devmode YES
log out, and log in back
press the key-combination that in your Mac shows the Dashboard
grab the widget you want to take off from the Dashboard, and drag it
press the key-combination that you used to make the Dashboard appear
drop the widget when you want to place it


Alternatively, there are some utilities that enable it for you; I cannot report you which ones are, though.