Hi cb,
All you need to do is:
-Goto your Admin Panel (when you are logged in there will be a link at the bottom) - you probably know this already.
-Goto 'Forum Permissions' under Forum Admin
-Here what you do is select a forum section and choose who it is visible to (public to everyone, registered users only etc) as a very simple way.
-Once you have chosen a section, select the advanced tab under that. Rather then set an overall permission to a user type, here you can control the individual elements, Read, Post etc. Here what you would want to do is change all of those to moderator, except for view - put that to all. (You may need to put read to 'All' as well)
However if you are using groups, which is really the best way to control your permissions, then add the people you want to a group say 'Normal User' and do the same as above but goto the 'Group Permission' link under Group Management.
The only thing you have to watch is which sections override which, im not sure offhand so you may want to test it out. I.e what if a user has Posting permission but is in a group that doesnt..
Hope that helps!