One thing that I really like about IE, but is not available in other browsers is the client side modal dialog.
A modal dialog is a popup window that must be acted on (or closed) before you can do anything else on the window underneath.
I came across a nice modal dialog being used on the forums.asp.net site. I ended up emailing the guy who wrote the editor I was using, and he directed me to the original creator of the dialog “submodal.”
It is still not clear to me if this technique will allow you to pass back a value from the modal dialog to the opening page, because I think that is a very important feature, but I don’t see any direct reference to it.