Thanks to the efforts of Joe Yoder and Ralph Johnson, the proceedings of the 2006 conference on Pattern Languages of Programming have been archived in the ACM Digital Library. I expect the 2007 and future proceedings to be made available through the ACM DL as well. Whether it will be applied to past years is unclear.
This applies to one of my publications right now, the 2006 edition of Value Object. The full reference for this paper is:
Dirk Riehle. “Value Object.” In Proceedings of the 2006 Conference on Pattern Languages of Programming. ACM Press, 2006. Article 30.
Please note that no page numbers are given, only an article number. It appears that thinking is shifting from a pre-electronic area type of publication to an everything-online service. I’ve never cared about page numbers, all I’ve ever wanted is to quickly find articles. For that the article number in a given volume is more than enough!