The easiest way to explain GeoMaker is with this screencast:
In essence, using GeoMaker means going through four steps:
Enter the resource you want to analyse. This could be:
Filter out results that you don't want to have in your final map.
In any case, un-check the locations you don't want to show up in the final map.
Get your results.
Errors can happen, and we hope that we planned for each of them. If you do get a blank page or some very weird error, please contact us, explaining what you did to get this result.
Whilst GeoMaker tries hard to pre-emptively fix things for you, there are some things we cannot fix. These are:
If you find other problems, please contact us, however as GeoMaker is not our main job don't expect full service.
The easiest way to reach us is via twitter where I am known as @codepo8. You can also leave a post on the GeoPlanet forums to reach both Chris and the Geo team.
GeoMaker by Christian Heilmann, using YUI, YQL and Yahoo Geo Technologies - API