Some discussion about distributed and centralized version control system:

http://blog.ianbicking.org/distributed-vs-centralized-scm.html
http://blog.ianbicking.org/centralized-vs-decentralized.html
http://mail.python.org/pipermail/python-dev/2005-August/055372.html
http://www.drdobbs.com/article/print?articleId=240159530&siteSectionName=architecture-and-design

A shorter but still in-depth discussion - http://www.infoq.com/articles/dvcs-guide

Difference distributed SCM software: 
http://www.opensolaris.org/os/community/tools/scm/history/
http://bazaar-vcs.org/ 
http://www.selenic.com/mercurial/wiki/index.cgi
http://git.or.cz/

An introduction to git-svn for Subversion/SVK users and deserters - http://utsl.gen.nz/talks/git-svn/intro.html

For Mercurial, as some say Sun will use it for SCM of JDK http://blogs.sun.com/mr/entry/openjdk_scm , thus a lot of peoples talking about this - http://video.google.com/videoplay?docid=-7724296011317502612 and the book - http://hgbook.red-bean.com/hgbook.html
 
DVCS and DAGs (Directed Acyclic Graph)
http://www.ericsink.com/entries/dvcs_dag_1.html
http://www.ericsink.com/entries/dvcs_dag_2.html
http://www.ericsink.com/entries/dbts_fossil.html
http://www.ericsink.com/entries/merge_history.html

Making Sense of Revision-control Systems, WHETHER DISTRIBUTED OR CENTRALIZED, ALL REVISION-CONTROL SYSTEMS COME WITH COMPLICATED SETS OF TRADEOFFS. HOW DO YOU FIND THE BEST MATCH BETWEEN TOOL AND TEAM?
BRYAN O'SULLIVAN - http://queue.acm.org/detail.cfm?id=1595636