Announcement Plugin?

Looking to see if this exists. I'm looking for a plugin that will let me display announcements on top of certain points of my site. Basically this:

I want to stick a block of text above the top news story that says "You should check my Twitter feed too, as some short news bits and other discussion happen there".

Now I know I can just go into the template and hand code it in there, but I was looking for something more elegant than that. Something which would allow me to define what category(ies) it would appear in, what page(s), and possibly cool stuff like time/date ranges. That's where a plugin would be needed.

Does anything like this already exist in the wpmu group? I found something similiar to this, but given I belong here, I thought I'd ask here. Tkx.

Here's the "similiar" idea: