logging a user in programmatically

I've been using SecurityFilter for a while now with great success.   
What I would like to do now is be able to log a user in, so that the  
user is returned from calls to request.getRemoteUser(), without them  
sending us their password in a HTTP request.
   The reason for doing this is that I want the user to be able to  
check a Remember Me checkbox upon login so that whenever they return  
back, whether its a day or a week later, they can just be logged right  
in.  I've kindof hacked this into working by retrieving their password  
(we have to store the password in our db for other reasons) and place  
that into a URL that we redirect the browser to.  I don't like this  
solution and would prefer to give the user a cookie that we can use to  
look them up in our database, but still be able to have them get  
logged in with the web container (Tomcat in this case).
   Is there a way to do this?
   Thanks,
    -M@

-------------------------------------------------------------------------
This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
Build the coolest Linux based applications with Moblin SDK & win great prizes
Grand prize is a trip for two to an Open Source event anywhere in the world
http://moblin-contest.org/redirect.php?banner_id=100&url=/