http://modestmaps.com/
ModestMaps is an open source flash (ActionScript) library that displays tiled images (from google maps, open street map, and others). Similar but smaller /simpler than OpenLayers and in ActionScript not Javascript.
http://cloudmade.com/
CloudMade are a mapping technology company built by some of the people behind OpenStreetMap.org, using that data as a base. Professional open source mapping services.
