Login History adds a new table which stores a list of each users' past logins. This module was originally written as a way to capture a user's last login timestamp.
One thing I'd like to do but haven't yet – since the project I originally wrote this for didn't require it – is to have a threshold of how many previous logins per user are kept in the database. Currently, if the site has a lot of users, this table could get rather large.
This module is in early development. If you have any ideas for improvement, please post in the issue queue. Better yet, submit a patch! :)