Oxford University Press and JAMS
In honor of National Library Week in the US, Oxford University Press is offering free access to online OUP products (excluding journals) during the week of 13-19 April. This includes Grove Music Online and the Oxford History of Western Music.
Username: libraryweek
Password: libraryweek
http://global.oup.com/academic/librarians/national-library-week/?cc=us&lang=en&
(Although it says access is available in the US & Canada, Grove and OHWM seem to work from here in Germany.)
JSTOR is also offering free access to the Journal of the American Musicological Society today:
http://www.jstor.org/action/showPublication?journalCode=jamermusisoci