Last Logon

Is there a way to find out when a particular database user last logged on to the database? I have severl ahundred database accounts whose owners I don't recognize. Some of these users might have left. I want to delete unused accounts. How do I find out? Thanks.

I'd create a logon trigger that fires a row into a table containing the username and logon time etc of each user. After a month or so you will have a feel for which users are redundant