Yahoo has released a new product called Pipes that looks like it's essentially a tool for making mashups.
Library bloggers, notably Aaron and Sarah, have posted a bit about it. There's not much by way of official help or documentation yet, but other blogs (like Mr. Speaker, Frantic Industries, and David Rothman) have posted some ideas.
Even after reading all that, I still felt like I needed to try it to really get it - so here's my first attempt: MADreads - Nonfiction reviews.
I took the RSS feed for Madison PL's book review blog, MADreads, and ran it through a filter that shows only the nonfiction reviews. The "pipe" can either be viewed as a web page, or subscribed to as an RSS feed.
My example can hardly be called a mashup - and it's technically not doing anything the blog authors couldn't do with category feeds. However, it was something I could do for myself as a blog reader, without knowing anything more than the RSS feed and the name of the categogy I want to see.
It's going to take a bit more figuring to see what kind of useful stuff Pipes can put out. A commenter at Librarian in Black described how she's using it to email blog entries to non-blogreading colleagues.
(Next I think I'm going to put a filter on my Chowhound forum feed to strip out everything that's not about Wisconsin. And maybe throw my Yelp feed in there too, and get rid of the non-foodie reviews...hm...maybe there's something to this after all...even if it's only for amusement, or to improve the nutrition-to-filler ratio in my personal information diet.)
Try Pipes for yourself, and comment if you can think of a good use for them!