I caught a piece in the mainstream media today about Netmums opening up their "Parent Bloggers Network", a section of their site to which bloggers add their blog details. This then seems to allow short snippets of blog posts to be listed on the Netmums site (presumably via RSS?) and the blogs themselves to be viewed in an iframe.
Something like this would be useful for my niche too but I'm struggling to find any links to software which would allow me to add this functionality to our existing domain (I'm not even sure what to call it - a blogging network? a blog aggregator? a multiblog portal?)