OpenStreetMapOpenStreetMap is a wiki map of the world. The Cincinnati area has some transit lines entered, but the map is not complete. If you know what you're doing I encourage you to add to it, and if not, to learn!
Other Regional Geo-spatial Data
Elevation900 MBThis has a couple GeoTif files with elevation data in meters. One is very high resolution and centers on the city. The other has a much larger extent but a lower resolution. Both were derived from USGS data from 2006 and 2009. Go to USGS if you want the most up to date data and for a national extent. I provide this here because it was somewhat difficult to find all the data I needed for a regional map and I figure I might save someone some time by sharing my work.
OpenStreetMapOpenStreetMap is a wiki map of the world, and Cincinnati is surprisingly complete. Actually, quite a bit more so than Manhattan. Anything that can be mapped can be mapped here, all in the same dataset, and probably has been by some truly nerdy local cartographer. It's more complex than a shapefile though, so if you aren't comfortable with command line programs and SQL this may not be for you. I recommend BBBike.org to extract data for the Cincinnati area.