I like Jeff's suggestions for a Service Oriented Lanugage as well as RebelGeekz' idea of how to include XML Infoset information in a language without resorting to angle brackets. I wonder what a community developed lanugauge would look like? I've experimented with Coco/R which really reduces the effort it takes to build a parser. Of course, the language design and code generation are the hard parts!
Source for Coco/R is available on the Rotor Community Projects page. Other cool projects include a port of Rotor to WinCE, two different AOP projects - one for C# and the other language neutral and a set of improved collections.