Joey Hess, a famous Debian hacker, wrote long ago an article about how he was keeping his entire home directory under version control, using CVS. Now, as CVS gets replaced by Subversion, he switched to it, and new article was released.
He gives advice on how to split private and public projects, how to keep configuration files under version control, how to use the same home directory on multiple machines. Of course, main advantages of described approach are distributed backups (including inherent mini-backups in form of file copies in the .svn directory); history of your work and configuration changes, including rollback and comparisons; and single synchronized workspace across every machine you’re using.
Read more at OnLamp: Joey Hess “Keeping Your Life in Subversion” or at his blog: joey: “Subverting your homedir, or keeping your life in svn” (contains extra links and updates).