I 2nd the MAL option. There is also a PC software that helps you auto update whatever you have watched to MAL @ MyAnimeList.net Updater Software
I wouldn't recommend using it if you are concerned about privacy though, as it sends the title of whatever you are watching over to MAL for searching if it isn't on any of your anime list.
I have been using it for years without issues tho. My current watching list - Darkonlore's Anime List - MyAnimeList.net