RSS widgets have been around for some time now. But what I like about RSS Mixer is that not only can you roll several RSS feeds into one, the utility also provides the code to embed it as HTML, widget or iPhone format.
I added a widget to my blog’s side bar today (look far down on the right) that pulls in just one feed from PLCMC’s Readersclub, but I could have rolled several feeds into one. I think the the most powerful use of a utility like this may be in sharing the code for widgets themselves (already created and formatted, of course) with users. This way they can easily grab it and embed a bit of the library in their own online spaces.
There’s so much potential for libraries to unshackle our content and make it available in “syndicatable” (don’t think that’s a word, but I can’t at the moment think of a better description) formats. Widgets seem like a natural way to engage users in promoting libraries' online services.
On a related note, both HCL & PLCMC now offer catalog widgets and I just noticed that there are ten libraries in Facebook with catalog apps.