I have a simple table that lets me know when users log in and log out and to which main layouts they travel.
For sorting sake and for keeping data separate, I store in global variables (and some global fields) such things as last name, their grade, subject, the school they teach at and the type of user they are (the type determines the navigation bar they see).
What other information do you capture when people log into the database? I assume some people do a preferences logging?
I love watching and graphing the number of logins. I'm proud to say in 6 weeks of using the database, the 90 users have logged in over 7000 times (though sometimes its one person multiple times in a row). Its silly, but i like to see that number grow.
What other data do you capture when people are in your system?