Not a plugin but rather an add-on, this remote service no ads, no banners free guest book, is nice when used on Static Pages using iframe. You can customize it in any language and the site have several templates available for colors. You can see it working here
and you can find it here

what I'd like to see is have someone add comments to static pages and allow the site admin to turn then on or off on a per-page basis, the same way I have done with user pages. I should actually request this on the dev site. Actually, I'll do it if someone tells me they'll put it in the base code.