Two separate blogs- how to?

Please advise me on how I do this- I want to be able to have to separate blogs:

-1 for the admins of the site only ( that i wish to keep as this page: http://community.learnhebrewtogether.com/wordpress/ourblog)
-and one that allows postings from all community members.

Should I use a plugin. If so can you suggest one or two? Or is there a way of doing this with the existing blog facility settings?

Thanks very much!

Kind regards

Maria