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You could use an <iframe> and a javascript function with a setTimeout that changes the src of the iframe every five minutes. The user would still be able to click around the sites and as long as none of them have a frame-breaker, every five minutes it'd be like they suddenly were moved to a new site without clicking anything.
If you had the container page exposed, (like with a visible toolbar) you could also display a countdown timer to when the next "jump" was set to occur.