Creating a WP Blogs Portal

Hello.

I'm trying to build a community of bloggers and I've setup a WP3.01 MU install. Them all are friends, family and some pro writers; closed to public.
Blogs are running, plugins work and themes are doing it beautiful.

The only I need to do is to setup a main page for the blog system/network. I have a main blog, owned by the superuser, and I need themes, plugins or whatever else to have
- the 5 (i.e) last published post with title, photo and excerpt in any blog
- the 5 (i.e.) last comments on any blog
- a category-driven directory with each blog

I can't see the forum charts so I think I can post links (please, moderator, delete this if it is not allowed). I'd like to have something like that:
http://lacomunidad.cadenaser.com/
http://www.momblognetwork.com/

What is the correct theme or plugin or both or what is the CSS tric to build something like this.

I really appreciate your help because I'm almost one mont out of date.

Thenks in advance.