I love how Atahualpa allows one to allow sidebars on types of pages, but is there an easy way to tell it to only show a certain defined sidebar for a single page?
I know I could exclude all the page IDs except the one I need, but that would take all day and I would constantly need to update the exclusion list every time I create a new post or page.
Essentially what it would compare to would be an option that would say, "Turn right sidebar ON for only these pages" instead of "Turn sidebar OFF for these pages".

An option may be to tag the page with a special tag like "sidebar3" and put some condition in that only shows the sidebar if the page carries a certain tag. Hmmm, not sure how to go about that, though.

try the 'widget-logic' plugin http://wordpress.org/extend/plugins/widget-logic/