Just finished writing small SEO case study of About.com here. I hope it will help you guys. If you have some pointers to add then please do tell me and I will add them
i have read it really it is great study i will back and i have some additions it will help you Conciliation_
Good, but you forgot two of the most influential factors about their rankings. #1 Massive use of subdomains, each topic is setup on it's own keyword subdomain. #2 Spiderbites yes, the whole don't make pages for spiders is out the window with their Spiderbites Pagerank funneling: http://spiderbites.about.com/sitemap.htm