Posting to multiple sites.

[HortiTrends]

Is there a better way way to post to multiple sites through my
Posterous dashboard such as ticking a box to whichever of my sites I
want a particular site post to go to.

Also is there a way to take Posterous and embed it in my own site. I
am developing a directory portal for horticulture companies. Rather
than a static information site companies would sign in to the
directory and update or comment or place news articles there.