WordPress MU

I realize this has been covered in previous posts, but reading through what my searches came up with I still feel uncertain how to achieve what I want.

I have three domains hosted at the same place using www-forwarding between folders. I want to set up three not-quite-separate blogs ideally using one installation and one admin panel.

Let's say my domains are domain-one.com, domain-two.org and domain-three.net
The ideal situation would be if I could post to domain-one.com and tick off whether the post should also be posted on domain-two.org, domain-three.net net or both of them.
A diagram of what I mean here.
Is this achievable with wp-mu, and if so; How?

Apologies if this is something obvious, but I really couldn't deduce from the searches I did.

My suggestion, might be to much hack for you, but you could have three different WP installations (not WPmu), that share userbase and contentbase (and other tables), and then according to categories, you only show specific posts at the different domains.

I've done this with succes for some subsites, and technically speaking, a subsite and top-domain is no different (might be some differences with cookies - maybe).

Yeah, I agree. Would be much easier to accomplish what you want with regular WP.

MU doesn't allow (so far) for cross- blog posting.