I like the IMDb Movie Collection Manager - by Futuros
http://userscripts.org/scripts/show/36797 Greasemonkey script. It does auto-highlighting of IMDB pages (or any page w/ IMDB links) of movies you've either rated or added to MyMovies lists. This is better than just adding movies to a list like next-flick.net. Next to every IMDB movie will be printed your rating of it, the list you've moved it to, and a drop-down arrow to either remove it from that list or move it to another one. So its like you can write notes next to each movie on the page. I have an "Awaiting Viewing" list that I take movies out of once I've rated them, a "Not Interested" list for movies I've watched the trailers for and want to remember to avoid, and a "Blu-ray release upcoming" list to keep me from watching a DVD when I know there will be a blu-ray version. Its easy to go through actor's and director's pages and see the status or research you've done on a film at a glance. And when you do keyword/MoKA searches, you only need to examine the ones that don't have highlighting marks of some type on them.
Likeminds
http://www.likeminds.com looks promising due to its ability to automatically transfer your ratings between different sites like IMDB, Netflix, Flixster, and Rotten Tomatoes, but its still prone to errors as too often it can't match up movies between the sites.