The ASL project is run by Adobe where it is an attempt to create a cross-platform GUI library. It uses pure C++ with many advanced concepts being used. The GIL (Generic Image Library) part of the project was recently accepted into the Boost project.
The ASL Wiki has a fair amount of interesting information. On the Supplementary Documentation page there is some interesting links, especially the coding guidelines information.
The Papers and Presentations page has some interesting C++ tidbits.