An Oxford University Press announcement says:
Celebrate National Library Week!
All OUP Online Resources are free April 13-19th
Libraries are a vital part of our communities- they feed our curiosity, bolster our professional knowledge, and provide a launchpad for intellectual discovery. In celebration of these cornerstone institutions, we are offering unprecedented free access to all our Online Resources* [*Excluding journals] to support our shared mission of education. [...] No registration required- simply use the credentials below!
The free access starts on April 13th and will run through the end of the day on the 19th, running for the full duration of National Library Week. Access is available in the United States and Canada only.
The full list of resources is at the link; it includes University Press Scholarship Online, Grove Music Online, the Dictionary of National Biography, and of course the OED. Sorry about the geographical restriction, but for those of you in the US and Canada, enjoy the week!