I'm working on a web-based front end to an ERP-system at the moment. Suddenly the idea struck me that one could make "real" tab-control like interfaces by putting iframes inside css-layers. You can change tabs by hiding or showing the individual layers.
The cool thing about this is, that you can switch between independent HTML pages without loosing the client-state of the preceeding page. You can aboviously do this using multiple windows or frames, but it feels much better with a single window.