I am setting up a site for a client and have included a dynamic sidebar in the template for certain types of posts. I would like the client to be able to add a text widget to that sidebar for a post and put in content related to that post only. Is this possible in WordPress or is the text widget put in one post going to show up on all others?
take a look at Sidebar Generator it lets you specify a sidebar on a per-page/per-post basis.
some of its main features are: