url:rest AND url:arcgis AND chicago
I found interesting map layers from cmap.illinois.gov and Loyola Univ. But guess what... not a single word of descriptive metadata was published with any of these map services. The Loyola server is obviously used by students, so I can understand why there's no documentation. But the .gov GIS server is public-facing and, I would assume, authoritative. But I can't really tell. Can't tell anything about any of these services.
Maybe the map service authors couldn't figure out how to get information into the REST catalog fields for these services. It's not straightforward when publishing to ArcGIS Server.