Plugin – Change Select Menu

First off I must say: I love WordPress! Good software, loads of plugins and an seems to have an awesome community.

For the last few days though, I’ve been looking for a plugin that I can’t seem to find… This is what I want to do:
My site will have ‘sections’ you can click (combobox or something), which results in changing the side-bar hrefs depending on the section. This ‘section view’ remains until the user leaves or changes it again.

I also tried to look for ways by changing the selected menu.. Without any luck..

Originally I thought WordPress would have something similar, but I can’t find anything that comes close. :/ I was wondering if you guys might know some plugin or a way to easily do this? Or some advice on how to code it..

Thanks in advance!