If you have it, Quicktime Pro can do this, but you will also need a .Gif creation application, like the free
GifFun. Create a new folder in a suitable place on your hard drive, maybe call it "Image Sequence" then open your chosen movie in Quicktime Pro. Under "File" choose "Export" here you have a few options depending on what you need the end .Gif for.
This will export your movie file into a sequence of images into your created folder, and name each file sequentially, how many depending mostly on the length of the movie and also your chosen frame rate. If you do this in reverse it is a way to convert a sequence of photos into a movie for example.
Next you will need to open
GifFun, import your folder of images and create a .Gif for the web.