Ajax or CSS window loader plugin recommendations

I’d like to be able to load content in a separate div by using a drop down menu of urls. An Ajax plugin has been suggested, but I can’t seem to find one that would do what I want. Any suggestions?

Here’s some more detail: I am using a calendar plugin that displays different calendars using a short code. I’d like to load a specific short code in an active window so it will display a specific calendar. I’d like the user to be able to select the calendar using a dropdown menu that’s outside the active window.

Suggestions?