Blacktrash have a nice demo of the kind of functionality we needed but it wasn’t quite generic enough to manage our very different sized videos. The code below, based on this example using Flowplayer and jQuery Tools Overlay, is simple enough that you can easily add multiple videos to a page. The size of the video player is determined by the html5 style attributes “data-width” and “data-height” on each “a” link which are picked up by jQuery and used to resize the player. If you do not specify these then the default is used, as given by the CSS.
You can do a lot more with flowplayer and overlays so this is just a starting point but the approach is generic enough that any of the web team can add nice popup videos to a page just by adding a simple “a” link.