JavaScript Switch Content

I've been driving myself crazy the past couple hours and can't figure this out. Here is what I need to do:

Have a select box like this:

<select name="dropdown">
<option value="option1">option1</option>
<option value="option2">option2</option>
</select>

Then when one of those options is selected, the appropriate div tag is displayed:

<div id="option1">
Div 1 Text
</div>

<div id="option2">
Div 2 Text
</div>

This seems like it should be really simple to do, but I can't figure it out.