This archive is a collection of optical images. Like the Lung Cancer Alliance archive it is also hosted using Kitware's MIDAS archive software. This archive hosts 6 top level "communities" which contain anywhere from 4 to 242 items within them. In this case it seems not all of the data is DICOM but some of it is. Three of the Communities appear to be unrelated demonstration collections not tied to OSA as they contain lesion sizing data sets of lung images.
WebMIRS is the National Library of Medicine's (NLM) tool used for hosting two related datasets and related spine x-ray images which are part of the National Health and Nutrition Examination Survey (NHANES). The site requires registration and login through a java web client to view the data set. Most of the data is text based, but there are spine x-rays for some of the patients. The client allows for searching but not really browsing. The user must enter a boolean search query in order to retrieve any patient results. It does not appear that it is possible to actually download the images, rather that you can only view them in the WebMIRS client.
National Alliance for Medical Image Computing (NA-MIC) Image Gallery: http://www.na-mic.org/publications/gallery