Need help finding a particular plugin

Hi, I’m looking for a plugin that lets me publish a block of text (like a text ad or a note) that always appears – for example – after the second post on my blog. The text block stays in the same location even as new posts are published (meaning, it always appears after the second post).

I know I’ve seen this plugin somewhere, but I can’t remember the name of it, and for the life of me I can’t track it down.

Anyone know what I’m talking about?

Thanks,
Susan
http://www.mysouthborough.com/