Ok, so Steven Cohen addressed my question (ok, I'm a little embarrassed) about restricting the posts you get from a particular feed to those containing keywords or sentences of your choosing: it can be done in PubSub. I just built 4 subscriptions. Now I just have to wait and see what happens.
PubSub defaults to an OR operator between terms, which is pretty logical here IMHO. I didn't see any mention of truncation (I may have missed it -- I'm kind of impatient) so I just added as many variants of words as I could think of. And they've even set up a group of library weblogs, so happy librarians can filter feeds within their very own circle. Just 'focus your subscription' on 'weblog entries' and check off 'The Librarian List'. Super! There's a 'Comics List', a 'Fashion List' (Lorie?), a 'Law List', a 'PR List', and a 'Real Estate List' too.
More info on PubSub syntax here.