FindMyPast.com is providing free access this weekend at both its US website and its UK one. I believe their site is most useful for its UK parish and military records (including Ireland), but there’s lots of other data. The free access requires registration (name & email) but not a credit card. It starts 5 AM Arizona time this Friday the 6th, and runs until Monday morning.
See this Dick Eastman blog post for further details. Thanks to Pat Menon for letting us know about this.