A Pure CSS Solution
This may or may not work depending on the situation, but you can actually mimic a drop-down menu's behavior with css selectors in IE8 and up. Here's an example. Click on the menu, and as long as you hover around the content the content will appear, no javascript required.
Functionality
By default, all the content is hidden. However, thanks to the :active pseudoclass, you can change the content to display when the parent is clicked. This is pretty inconvenient though - the user has to hold down the mouse to see anything. However, we can cheat a bit - by adding a :hover pseudoclass that displays the content, if the user clicks and hovers the content will stick around.
So far, we have this css:
.container.content {
display: none;
}
.container:active .content {
display: block;
}
.content:hover {
display: block;
}
This is a little flaky though - you have to move your mouse down over the content to have it persist, and will likely confuse. We can cheat a bit though by making the content larger than it appears. A simple way to do this would to be just to padding (that's what I've done in the example I added), but this can cause some odd reflow issues. A better way I think is to add deliberate spacing divs that add to the size of the content without changing the flow.
If we add this
<div style="position:absolute; top:-50px; height: 50px; width: 100%;"></div>
to the start of the content, there's an invisible div hovering over the menu, which will extend the area on which hover works. A similar thing can be done to the bottom, leaving us with a solution that has a larger hover area, and doesn't trigger reflows beyond the main content.
Remaining Problems
Anyway, this isn't perfect since it certainly isn't as flexible as javascript. There's no sliding, and you can't reliably make the content show up if the user mouses out.
As other people suggested, you can still improve this with javascript after the fact should the user have it enabled though - this can still work as a decent backup to noscript users.