I think it's called RSS feed. :p

When you update your main blog, there are RSS-feed utilities that will swipe the new RSS feed info and automatically add it to other sites.

FWIW ... replicating content like that is cheesy, IMO. It's much better to come up with original content, at each site.

(What's wrong with Cut-n-Paste + paraphrasing?)

Don't know of any blogging packages that do this, but there's a bunch of RSS feed utilities that do this.

Rots of ruck.