ESRI is an industry leader in the GIS space, and their ArcGIS Server provides Internet and Web oriented GIS and spatial data services for your own applications. ESRI has created ArcGIS API for Flex to allow Flex developers to leverage the power of ArcGIS in their own applications. The API is in beta now, and there are lots of nice samples posted online. Thanks to Jason Harris for bringing this one to my attention.
PS Did you notice that the ESRI sites linked to above are powered by ColdFusion?