Never memorize something that you can look up. -- Albert Einstein
'phillw' on #lubuntu (irc.freenode.net) pointed me to this post on ubuntu forums.
To switch between 'standard' QWERTY and DVORAK layouts:
setxkbmap -option grp:alt_shift_toggle us,dvorak
This assigns ALT+SHIFT keyboard shortcut to switching layout between QWERTY and DVORAK.