So how do you transfer your photos from the iPhone 3G to your laptop running OS X if you don’t have iPhoto app? — Easy, just use the buit in app called Image Capture.
The app can be run from: Finder -> Applications -> Image Capture
Now, you can either download some or all photos by clicking on either one of the bottons as shown in the screenshot. Remember that you should have the iPhone connected to your copmuter, otherwise you would see the message saying the no device found or connected.