Blogs created dynamically by users?

Hi newbie here to WP, but itching to be hacking… is there a way or has anyone created a site where members can create their own blogs dynamically? These would exist for a period of time and then be archived…

I wasn’t sure where to start with this, so Miscellaneous seemed like a good a place as any…

Very much appreciate any comments and pointers (in the right direction…).

Thanks in advance.