Tools for comparing/synchronizning directories

Komparator
http://sourceforge.net/projects/komparator
http://polishlinux.org/kde/komparator-a-comparing-tool-for-kde/

Meld
http://meld.sourceforge.net/index.html

Unison
http://www.cis.upenn.edu/~bcpierce/unison/

Kdiff3
http://kdiff3.sourceforge.net/