IronScheme is now open to the public :). You can get more details @ IronScheme on Codeplex, the current source code is available via the source repository on Codeplex.
IronScheme replaces IronLisp, and has been a partial rewrite IronLisp. Currently IronScheme is at the same functional level where IronLisp left off, excluding support for .NET interop currently. The main focus is R5RS compliance (well as far as I can get to it).
Currently, the most significant part that lacks for R5RS compliance is a decent number system. It only supports ‘double’ and ‘int32′ for now, but I plan to support the entire number tower, if possible.
There also has been some improvements, especially the interactive console, and the ‘extensibility’ model of IronScheme. Tab completion is now available on the console, as well as pretty colors for errors, evaluation result, etc.