Culture Hack Day
There's going to be a Culture Hack Day in January, the weekend before History Hack Day. They're like buses; you wait for ages for one to come along and then two show up at once.
openhacklondon | Open Hack 2009: London
The next Yahoo hackday will be on May 9th and 10th in Covent Garden. I've registered my interest. You should too.
Related links
A Hack for Europe! (plasticbag.org)
Registration for Hack Day Europe (June 16th-17th) is open. Sign up now! This is going to be a lot of fun.
YUI’s Matt Sweeney and Hands-on YUI Workshops at Yahoo! Developer Day/Hack Day September 29-30 in Sunnyvale » Yahoo! User Interface Blog
Yahoo is opening up Hack Day to the masses. If you're anywhere near Sunnyvale on September 29th, this should be fun.