Dont forget: Trejdify - business news only (http://www.trejdify.com/)

Inbound - SEO/marketing only (http://inbound.org/)

Not simple aggregation per-se, but http://dev.newsblur.com is showcasing a much more intelligent approach to social news discovery...

Completely self-serving - but I do see my project playing into this space. http://knowitapp.com