Adding External Blogs ?!

Hi ..

Im new here and wish you can help me. Im trying to build a blogging network for my colleges in medical school, i know that wordpressMU in the best script for this, but im looking for something that i dont know if wordpressMU can do it, i want to add users with external blog (wordpress blogs on different domains and if i could also add bloggers blogs that would be great to), so can i do this and then aggregate there new posts and new comments on the blogging network ?!

Thank You