jQuery Impromptu

This.

Forms online are where the rubber really meets the road in terms of online usability. It is a place where you have to make a really strong case aesthetics-wise to start showing users something unfamiliar. (Not saying that the case can't be made, just that it's a hard sell to usability-centered designers like me.)

I really like being able to use Javascript's prompt() and alert() dialogs (when the case really calls for a popup, of course) for the reasons you describe. But it seems like some browser vendors are pushing to make them as cumbersome as possible. Internet Explorer, for instance, will alert the user with a security warning if you use prompt(), saying "This page wants to ask you for information from a script" or something like that. I've encountered quite a few people who think that's a bug in my site's code.