The Mass Observation Project (handily abbreviated to MOP) has been chronicling the everyday lives of UK residents since 1937, providing once of the richest sociological archives around. On the 12th of May this year, people are asked to write about their day, no matter how ordinary or extraordinary, and share it with the MOP archive, for future use by researchers and others. An amazing resource for a glimpse into the personal lives of thousands of people and therefore a sociological diamond.
To participate in the 12th May diary day, you must be living in the UK, and able to write about everything you did that day - stuff like what you talked about, what you ate and drank, what you bought, your job, the places you visited and people you met, how you felt, what you thought about, etc etc. Add to this a peppering of demographics, like your gender, age etc. to locate your contribution within a particular context, although make sure nothing is identifiable.
Further details, plus the template and the MOP agreement, are available from the MOP website.