At the Compiler DevLab that we hosted a couple of weeks ago, we threw together a quick starter kit for folks interested in building languages on top of the DLR. You can grab a copy of ToyScript here.
The DLR experiences presentation that I gave at the DevLab is probably the best source of docs (outside of the IronPython 2.0 Alpha sources) for folks interested in building a compiler using the DLR.
Update: fixed the link to the DLR Experiences talk.
