Grant Curtis, the producer of Spider-Man 3 reveals on his official blog that a new trailer will be released this fall:
In regard to the next time you will get a glimpse of the movie, please know that we will have a trailer coming out this fall. Although I am not at liberty to say when exactly it will hit the theaters and internet at this time, I can tell you that I have seen a rough version of it and I am confident that you are going to be blown away. It is an incredible piece that showcases the full scope of the picture, both in terms of the gripping story as well as the groundbreaking visual effect shots. Be patient, it's going to be worth the wait.
Curtis discusses other matters concerning the film and you can to read the entire blog post.
Spider-Man 3 was released May 4th, 2007 and stars Tobey Maguire, Kirsten Dunst, James Franco, Thomas Haden Church, Topher Grace, Bryce Dallas Howard, Rosemary Harris, J.K. Simmons. The film is directed by Sam Raimi.