ESRI webservicesESRI, one of the really BIG guns of the GIS industry, has stealthily released a public, non-commercial version of their extremely cool ArcWeb Service. as far as i can tell there aren't any limitations to its use beyond that it be non-commercial and they promise that it will be permanently free of advertising. we've used their SOAP APIs to talk to ArcWeb from coldfusion--it was a breeze. you can see more info here
and while we're a dyed-in-the-wool ESRI shop, this is pretty cool.