I'm on a PC, but with my Bionic, there are two DCIM folders. One's on the phone memory (DICM) and the other is on the sd-ext (dicm). The pictures I've taken are in the sd-ext area (note that the folder name is in lower case).
You can also use Dropbox, EXTREMELY useful for getting a lot of pictures on your phone to your computer wirelessly with almost no hassle. I assume it works on mac since it's an iPhone app as well. Probably a stupid question, but I'm assuming Zumocast doesn't work with Apple products??