[plt-dev] promoting unstable libraries

About two months have passed since the creation of the unstable  
collection. I think it's a good time to have the first round of  
promotion discussions. The idea of unstable is to give facilities a  
temporary home in a public place while the interface and behavior  
settles down. Once that happens, they should move somewhere more  
permanent.

This thread has two goals:
   - select things to promote out of unstable, and
   - determine where to put them, including possibly creating new  
libraries.

Please respond with proposals of libraries (or parts of libraries,  
even individual exports) that you think are ready to be promoted.  
We'll start out with an open discussion, and I'll moderate if it seems  
necessary.

Ryan