Well, you added me, so I'm on your friends list.
If you go to your friends page (
www.deviantart.com/deviants/) you will notice on the right side of the page that you can create folders under "Deviant Lists." You can use whatever folder names suit you and then move a friend into that folder (using Add a Deviant). I organize friends by location, so I create a folder for each country where I have a friend. When I add someone to my watch I put them into the proper folder.
One might also sort friends by categories such as "Photography" or whatever.