Another option - free for personal use as long as credit given -
http://www.http//www.yxscripts.com/ - current version is IIRC G5.
I have used this quite a few times and it is very versatile - it's a mix of js and CSS - the latter enabling a lot of flexibility with appearance.
To see an example visit my wife's site -
http://www.thistlebees.com/ which will give you an idea as to how it performs.
It is possible as well - using CSS o its own to achieve this result - employing unordered list approach with CSS control over position and mouse actions etc.