Multi-user NOT multi-site

I’d like to allow multiple users to sign up to my site.

I don’t want each user to have his/her own blog with posts and pages – I just want users to be able to create posts which will appear in the main blog. I’m also conscious that my users aren’t going to be very tech-savvy so I need it to be simple for them.

So to me, it sounds like multi-site isn’t what I want. But I tried Buddypress and while it allows people to sign up, I couldn’t see how members could create blog posts. Plus it seems fairly big and slows my site down.

Is there a simple way? Or am I missing something really obvious?

Edit: I know I can manually add new blog contributors myself, but I’d like to allow people to sign up without pre-approval, but I would have to approve their first few blog posts.