Yesterday Google launched add-ons for Google Drive, suddenly making their online office product an awful lot more extensible. Lifehacker has a listing of some good tools to get you started, including information on how to create your own add-on, courtesty of Digital Inspiration.
Some of the existing add-ons that might be useful for libraries include the MailChimp Merge, some mind-mapping tools (don't you love meetings?) and of course EasyBib might prove useful for your students. Wonder what else we could come up with that'd be library-specific?