List postings within current category (plus title and excerpt)

I have all of my posts grouped into a hierarchy of categories. What I’d like to do is, based on the category the person is looking at, I’d like to generate a list of all the post titles, excerpts, and links in the sidebar. I know how to list it from a CERTAIN category, but I want the links to change based on whatever category the person is.

For instance. I have 5 posts classified in Writing > Technical > Reviews. When someone is looking at any of those 5 posts in Reviews, on the sidebar it should look something like this:

Other Reviews
[linked title review 1]
[excerpt]

[linked title review 2]
[excerpt]
…

It will NOT list any other items outside of the review category, including those in a parent category but NOT in reviews (like, news postings).

Similarly, an item in the news postings sidebar will look the same, only it will link relevant items in the news postings, and display the title “Other News Postings”.

I’d also like to limit my list to… say, 5-7 entries. And then just link to the category main page.

I’ve tried the SameCat plugin, but it’s not as versatile as I’d like. Plus, it gave me PHP errors.

Any help is appreciated, then you