Open Maps; customizable in so many ways

OpenStreetMap.org
OpenStreetMap is best described as the Wiki of Maps. It is a Free (both libre and gratis) source of maps and map data. Having free access to the data means you can download it to your own GPS device and have a much more detailed map than most come with. From their Wiki you can find out how to download whole states, countries, or the entire world. Most of the US is already on the map thanks to US Goverment data, but there are plenty of input errors that you could help fix. Just get an account on the site and click the Edit button, (play around first), and then edit for real.
OpenStreetMap unfortunately doesn't let you plan routes, although others take the data and let you do that and you can of course do it yourself.

OpenLayers is the javascript graphical interface used by OpenStreetMap and many online maps which let's you customize how the data is displayed, display overlays, and customize how it is controlled and much more.

I made a simple map using OpenLayers which shows the range of four Digital TV stations in the NJ area.
Note: I made up the range to be 30 miles, it is actually longer (or shorter) and has many other issues I didn't consider (antenna, obstacles).

I've been thinking of ways I could build on to this idea, perhaps in conjunction with my every other month or so check of what channels OTA DTV is providing my area. Would anyone else want to collect that kind of data on an every other month basis? I think we could store the data in OpenStreetMap (you can make your own tags) and then use OpenLayers to generate a map based on that data.