Although a lot of film fans and geeks like myself will tell you that "it's all about art and creativity" when it comes to filmmaking, I do like to check out boxOfficeMojo.com to see how much money current movies are making at the local multiplex. You can also dig into individual actor and director history and find out how one person's films have performed.
I was checking out Natalie Portman (hey, watch it) and realized it's too bad that BOM doesn't also track DVD sales and rentals. I see that Garden State did about $26 million domestic, but I'll bet it made a lot more on sales and rentals. The movie had a strong following (I know the sound track sold quite well on ITMS) but it seemed like the sort of movie that looked great but registered with most folks as a "Rent it later" type of movie.
(Oh, this is going back a bit, but speaking of Garden State, Zach Braff is still updating his Garden State blog)