The other thing I've been thinking about recently is finding a way of doing clever stuff with libraries. I know that many librarians are using OPML to cart library data around - and there are other specifications like MODS XML. Behind library data is a complex protocol called Z39.50, which seems to be a case of an inherently complex system that's been kept alive because nobody can be bothered to think of a better way of doing it (to my mind, SOAP/REST/XML-RPC and XML outputs have gotta be easier than this). There is a library file for using Z39.50 with PHP called YAZ. 
Indexdata.com have a guide to Z39.50 servers - check and see if your library is on the list!
David Walker has a project written in ASP.NET (and a port to PHP?) called Shrew.
Some of the folks at the Oxford University are working on making Z39.50 catalogues available via an XML API.
Library catalogues are currently silos. They've got kind of creaky, strange back-doors that make them possible to sneak in to, but they're silos nonetheless. Considering the valuable service that libraries provide, it's such a shame that for whatever reason they are siloed.
Perhaps I've got this wrong - maybe libraries are making their data available in a helpful and useful way for us mashup makers. If that is the case, it'd be one of the best types of corrections and one I would happily be given.
How do you want your library to provide you data? I'd love to be able to have a uniform search facility that would search all the libraries that I'm registered with and sort them by distance from me based on various location rules and settings (ie. if I'm in London, show me London libraries - if I'm at home, show me home libraries). Similarly, I'd love to be able to punch in a list of books that I'm looking for and have an RSS feed tell me when they are available - or when new books get deposited in the library that meet my criteria.
I'd love to have a Greasemonkey plugin that will show me whether the book I'm looking at on Amazon is available from my libraries.
I'd love to have a situation where I could be sitting in my word processor, and I'd be able to just type in the barcode number of the book I'm holding and it'd then build the citation for me.
We are still stuck in about 1986 with regards to the way that academics and students use technology. No doubt, the silo-building technology companies have really helped on that front... 
