What's cool at OOPSLA '05
JavariLanguage - MichaelErnst? presented a paper about JavariLanguage at OopslaOhFour, by the way.
Classages http://www.cs.jhu.edu/~yliu/Classages/index.html
This was cool. Modularity and encapsulation of Object Oriented mechanisms done right. Although there's little hope that such a language would replace Java or C#, hopefully future mainstream designs will incorporate at least some of these ideas. One fo the composition features in the language solves part of the ManyToManyChallenge.
TheProblemWithCheckedExceptions is finally addressed: http://www.cs.kuleuven.ac.be/publicaties/rapporten/cw/CW407.pdf
ScrapheapChallenge, an exercise in PostModernProgramming