OpenScales
OpenScales has been initially started from FlexLayers source code, donated by Scott Pezanowski. FlexLayers was a Flex port of OpenLayers. Since the beginning, the codebase has been extensively modified and improved. Nevertheless, even if OpenScales API is not strictly equivalent to OpenLayers one, if you have ever developed on OpenLayers, you will find OpenScales API quite easy to understand.
OpenScales Gallery
