The Internet Movie Database (IMDb) should be a familiar destination for all movie fans, because they are the only place online where you can find out about nearly every movie ever made. Even Netflix doesn't do that.
You can go year-by-year to find the top movies by boxoffice or MOVIEMeter(tm) rating, which is how I look for movies to put in my Netlfix queue, sometimes.
IMDb maintains a constantly-updated list of the top 250 movies by MOVIEMeter(tm). I would like to brag about how many I've seen of them. How do I keep track? I use 250films.net. 250films.net is a well-made site where you can actually check off the films you've seen. Click on this button to see which ones I've seen:
Here is another cool site for looking at the IMDb Top 250, where you can see monthly snapshots of the list going back to 1997, as well as do month-to-month comparisons to see which titles have been added or moved up or down.