Hi there Sadiq
A lot depends on the type of research you want to know about. Quite a few studies have used diaries in a quantitative way to collect information about how people spend their time. I like this article by Julia Johnson and Bill Bytheway because it really discusses the pros and cons and the practicalities of diaries:
http://dx.doi.org/10.1080/13645570010029467
There is an older Canadian study of nurses by Ross et al, 1994:
http://dx.doi.org/10.1177/019394599401600406
The increasing use of blogs means that they are a new source of diary type information. Here’s two examples of social worker diaries:
http://www.communitycare.co.uk/blogs/diary-of-a-social-worker/
http://fightingmonsters.wordpress.com/
Diaries are a good technique for conveying a sense of another person’s world:
http://news.bbc.co.uk/1/hi/uk/7421294.stm
They also give the participant an opportunity for reflection. However, you need to think about the practicalities of data collection. Not everyone feels confident enough or that they have the time to write things down. We thought about giving participants a recorder in one study so they could record their thoughts. However, everyone was too geographically dispersed for it to be feasible and so we are asking them to talk about their last shift instead.
It’s a while since you posted this so sorry if it’s no longer useful!