Dropdown Articles is a free module available free for all versions of Joomla, licensed under GNU GPL v2.
As the name might suggest, it's a fairly basic module that shows articles as a drop down list.
Listed articles can be restricted to one or more sections / categories. Article ordering is selectable.
Joomfish compatible*, core SEF compatible and sh404SEF compatible.
* at the time of the first release Dropdown Articles for Joomla 1.6/1.7 is not JoomFish compatible because there's no such thing as a JoomFish for J1.6/1.7. We will implement that feature as soon as technically feasible.