I looked into that before but couldn't find any good information. I was hoping you could put a noindex on a <p> tag and then close the </p> further down the page. That'd be nice.
I think if you used an iframe it might not be crawlable if you put a noindex in the meta of that iframe page, but that's messy.
I have never tested it though. Might be worth checking out. Discussion here about it
<iframe> Seo No No Or Seo Yay Yay? - High Rankings Search Engine Optimization Forum