I have made a couple of plugins and have another couple on the way.
First is really simple jp-bctl generates a bread crumb trail (of sorts).
Second is jp-links. It will attach relevant links to a post. Links are managed in a new link manager and are attached to the same set of categories as posts. The plugin then lists links in categories that match the current post.
Find them on http://jp.jixor.com/
Check them out if you want. Don't be too critical its my first go with WP. I mean I have used it before but never really done anything with it so I don't know it in and out or anything ;)