looking for stereo vision howto with 2 USB webcams

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Hi! I want to experiment with stereo vision in ROS Groovy using two USB webcams. I found the stereo_image_proc package with the ChoosingGoodStereoParameters tutorial. Unfortunately, it seems to be written to an older ROS version, and it doesn't work. There is an example bag file that should be used for the tutorial, but the images in the bag file can neither be seen in the rxbag nor in the imageview. Rxbag shows the timelines but no images. Imageview shows only empty windows, no images. I don't know why isn't it working and how could I make it work. Is there somewhere a working tutorial on stereo vision for ROS or can anyone explain how to use 2 webcams for stereo vision?